Barbara Lippert, Nicolai von Ondarza and Frauke Seebass

EU Enlargement: Ukraine as a Special Case – the Western Balkans as the Norm

Anchoring Kyiv in the EU through a New Type of Accession Association

SWP Comment 2026/C 17, April 2026

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ISSN (Print) 1861-1761

ISSN (Online) 2747-5107

DOI: 10.18449/2026C17

(English version of SWP‑Aktuell 16/2026)

Since Russia launched its full-scale war of aggression against Ukraine in 2022, the European Union (EU) has pursued its enlargement policy as part of a geopolitical approach. According to the European Commission and candidate states, the EU could admit new members from 2028 onwards, while Ukraine is calling for accession in 2027. Yet significant obstacles remain. Within the EU, the reform process designed to improve its capacity to act and prepare it for a Union of 30 or more has stalled. However, the readiness of accession candidates and the Union’s absorption capacity are key criteria that German European policy has traditionally upheld. There is currently intense debate within the EU regarding gradual integration, fast-track routes, and new safeguard clauses aimed at reducing the tension between geopolitical urgency and sound integration policy. With regard to the Western Balkan states, the EU should adhere to the well-established accession process. In the case of Ukraine, the situation is so acute that the political commitment to admit the country must be reaffirmed. As a preliminary step towards membership, the EU should offer Kyiv a new type of accession association that also includes a security and defence dimension.

EU Enlargement: Ukraine as a Special Case – the Western Balkans as the Norm

Anchoring Kyiv in the EU through a New Type of Accession Association

Barbara Lippert, Nicolai von Ondarza and Frauke Seebass

In the aftermath of Russia’s full-scale invasion of Ukraine, EU enlargement policy has gained new momentum. The Union now views the admission of new countries as a geostrategic investment in its own security. Montenegro and Albania are currently at the forefront of the accession process. Negotiations with North Macedonia and Serbia have stalled for different reasons. As regards Ukraine and, indirectly, Moldova, Hungary is blocking the formal opening of negotiations. Nevertheless, technical work on the negotiation chapters for both countries is being advanced. Bosnia and Herzegovina, meanwhile, has attained candidate status, while Kosovo remains a potential candidate. Accession talks with Turkey and Georgia – currently under a pro-Russian government – are de facto frozen.

A new northern round of enlargement is also looming on the horizon. Iceland’s government has announced its intention to hold a referendum in August 2026 on the resumption of its well-advanced accession negotiations, which it suspended in 2013. The European Economic Area (EEA) could thus come to an end; it is currently the EU’s only accepted and operational alternative to enlargement. Given these developments, expectations are that the EU could expand to 30 or more member states in the coming years.

The realisation of the ideal that a larger EU will also be a stronger one is contingent upon the successful navigation of two significant challenges. First, none of the current official candidates fully meet the “fundamentals” of the rule of law, democracy, and fundamental rights. This is an additional burden for the EU, which has itself become a weakened union of democratic constitutional states. Ongoing debates on how to incorporate more stringent safeguards into the accession treaties – extending beyond the established framework – are indicative of a deliberate policy to prevent backsliding on membership obligations.

Second, despite the urgency, the EU lacks the political will to undertake a structured internal reform process. However, it is imperative for the enlarged Union to assert its interests, security, and values autonomously in an era of great-power politics. The areas in which the EU must adapt are well known – whether due to enlargement or, more generally, to improve its own capacity to act and its legitimacy. At the centre are fiscal policy, the Common Agricultural Policy, and the Cohesion Policy, along with the fundamental legal provisions inherent to the Common Foreign and Security Policy and Common Security and Defence Policy (CFSP/CSDP), instruments safeguarding the rule of law in the member states, the size and composition of the institutions, and the decision-making procedures. These challenges are closely intertwined with the EU’s already extensive work programme for 2026/2027 (notably the reform proposals set out in Mario Draghi’s and Enrico Letta’s reports on competitiveness and the deepening of the Single Market), with the negotiations on the EU’s multiannual budget, and with its expanded security agenda.

Design concepts and instruments

Gradual integration, transitional arrangements, and safeguard clauses are instruments for admitting countries to the EU that do not yet – or may not on a lasting basis – fulfil all the rights and obligations of membership. These approaches are intended to safeguard the EU’s interests and its capacity to act.

Gradual integration

In order to provide candidate countries with an incentive and to swiftly reward corresponding progress prior to accession, the European Council adopted a policy of “gradual integration” in 2023. However, it failed to provide any guidelines on how the concept should be implemented in practice. Since then, the Commission has been exploring options that depart to varying degrees from the traditional methodology for admitting new members so far lacking a coherent conceptual model. Initially, forms of gradual or sectoral integration prior to accession were intended primarily to provide incentives for reform by offering candidates concrete benefits through partial integration. This refers, for example, as set out in the Growth Plans for the Western Balkans and Moldova, to gradual integration by policy sector, enabling participation in EU programmes. The EU supports and monitors efforts towards economic integration and the development of the institutions and capacities that are indispensable for participation in the Single Market – the cornerstone of membership – on the basis of the individual countries’ reform plans.

Through gradual integration, Brussels aims to achieve faster socio-economic convergence between candidate countries and EU member states, because the longer accession is delayed, the greater the divergence becomes. Early involvement in EU processes and programmes also serves a socialisation function. In addition, it is customary to grant accession countries observer status in the Council or the European Parliament during the ratification phase. These measures are intended to contribute to integration policy objectives of strategic autonomy, since the EU seeks to bind the accession countries closely to itself wherever it faces geostrategic competition, for example from Russia or China.

More far-reaching interpretations of gradual integration, aiming for Ukraine’s accession by 2027, have not been taken up by the Council. Proposals such as “staged accession” or “reverse enlargement” envisage granting a country only limited forms of participation in the EU system and its institutions on a temporary basis, either before or even after accession. This would result in at least a temporary restriction of the rights of new EU member states, thus amounting to a form of second-class membership. If, as is being discussed, a country were to be granted only reduced voting rights following its accession, for example in the Council, this would be discriminatory and hardly conducive to deeper integration. To date, no new member state has been required to accept such limitations.

Accession treaties and transitional arrangements

The EU has consistently incorporated provisions in accession treaties with new member states stipulating that, for a limited transitional period, derogations would apply to the principle of the full and automatic application of the acquis communautaire under primary and secondary law. However, these provisions pertained exclusively to policy areas and only to a limited extent to institutions and decision-making rights. They typically concerned, above all, the negotiation chapters on the four freedoms for goods, services, capital, and persons, as well as agriculture, transport, energy, the environment, taxation, and social affairs. For instance, during the 2004 enlargement round, the free movement of workers was excluded for a transition period of up to seven years. Typically, the EU takes measures to limit the costs in expenditure-related policy areas when new members join. For instance, new members receive only the full amount of funding to which they would be entitled from the EU funds on a phased basis. In addition, a cap is set on aggregate transfers, calculated as a share of the new member’s national gross domestic product.

Accession treaties also regularly provide for a general economic safeguard clause, a specific safeguard clause for the functioning of the Single Market, and a further clause covering criminal and civil matters in the area of justice and home affairs. In the case of Romania and Bulgaria, which joined in 2007, a special Cooperation and Verification Mechanism was applied, which remained in place until 2023. It targeted shortcomings in the judiciary and in the fight against corruption and organised crime. These were early forms of post-accession conditionality, which, however, proved not to be particularly effective. It is also important to distinguish it systematically from the differentiated levels of participation already built into both the Economic and Monetary Union and the Schengen system, which new EU member states can only join once they fulfil the respective criteria. In addition, the accession treaty for Romania and Bulgaria contained a clause with the option of a one-year postponement of accession, which the EU did not, however, exercise.

It should be noted that, within the framework of its traditional enlargement policy, the EU has numerous instruments at its disposal to address mutual interests and capacities, particularly with regard to the challenges faced by new members in adopting the acquis. What is serious, however, is that in the current process there is little confidence that the accession countries will adequately address the most significant shortcomings in meeting fundamental political requirements. Experience shows that the prospect of membership constitutes the strongest incentive for reforms prior to the completion of accession. Afterwards, the EU institutions’ ability to influence and exert pressure on member states diminishes. Following accession, EU actors can rely only on the existing instruments of conditionality (see SWP-Aktuell 50/2024). In preventive terms, this involves the rule of law dialogue within the Council and, in the event of breaches, the rule of law procedure under Article 7 Treaty on European Union (TEU), the rule of law mechanism for the protection of the EU budget, and infringement procedure, which make it possible to impose penalty payments. In particular with regard to political conditionality, the respective shortcomings of the accession countries overlap with those in the EU itself, underlining the urgent need for reform within the EU-27.

Suspension of voting rights after accession and new safeguard clauses

Measures are under discussion within the EU to ensure the capacity of the enlarged Union to act, including the possibility of denying new members so-called veto rights. Under such an arrangement, the states in question would possess no effective right to block – either temporarily or permanently – decisions requiring unanimity in the Council (such as on taxation, the CFSP, sanctions, or the budget). This is where the broader reform objective of extending majority voting in the Council converges with the interest in making vetoes more difficult to exercise.

Similarly, specific sanctions are under discussion to make the EU response more effective if a new member violates the Union’s values, as set out in Article 2 TEU. According to Enlargement Commissioner Marta Kos, however, such safeguard clauses are not intended to disadvantage new members, but rather to apply in the event of specific violations. Even so, it remains entirely unclear how this provision would be implemented.

Reactions to these proposals from the candidate countries have been mixed. On the one hand, advanced candidates such as Montenegro have expressed concerns that they may be subjected to lasting discrimination and treated as second-class EU members. On the other hand, the Albanian and even the Serbian government are signalling their willingness to agree to such a “deal” if it enables rapid accession while preserving the other benefits of membership. At the same time, it is improbable that those member states calling for fundamental reforms to safeguard the EU’s capacity to act would be satisfied with safeguard clauses alone.

The special case of Ukraine

Undoubtedly, the most significant pressure for reform within the EU stems from the prospect of Ukraine’s accession. In the case of the Western Balkan states, unresolved conflicts and external influences do pose problems, but these are not comparable to the difficulties experienced by the eastern candidate countries, Ukraine and Moldova. The expected financial transfers to the Western Balkans are considered to be manageable, as the combined population of the countries concerned is approximately 16 million. Iceland, too, as a potential net contributor, could be integrated using the traditional method with only minor adjustments.

The accession of Ukraine, which has been profoundly affected by Russia’s ongoing military aggression, would, however, present a challenge of a different nature, and even more so if it happened as an “emergency accession”. The geopolitical ramifications of the war may result in the introduction of a novel enlargement methodology and a new form of EU membership. Much depends on the terms of the ongoing negotiations to end the war (in which the Europeans are involved only indirectly), and equally on the future status of Ukraine’s sovereignty and territorial integrity. Political or even legal commitments regarding Ukraine’s rapid EU accession are on the table. This is one reason why the Commission has raised the prospect of “phased integration”, or reverse enlargement. For Ukraine, this would amount to a purely nominal accession with reduced rights and obligations, after which the country would only gradually achieve full membership.

Kyiv has stated its intention to conclude the negotiations – which have not yet officially begun – by 2027 and can already point to impressive progress in aligning its legislation with the acquis. At the same time, Ukraine continues to face serious shortcomings in terms of resources and administrative capacity, as well as in the enforcement of legal provisions by supervisory authorities and the judiciary, affecting all relevant policy areas. This is also linked to the severe deficits in curbing corruption and meeting other requirements from the “Fundamentals” cluster (see SWP-Comment 15/2026).

Ukraine’s accession prior to full alignment with the EU acquis would represent a significant departure from the accession methodology applied to date. Rapid accession would also be difficult for the EU to absorb. The strain on its budget alone would be substantial, according to current calculations – in Cohesion Policy due to the special circumstances of reconstruction, and in the Common Agricultural Policy because Ukraine would increase the EU’s agricultural area by a quarter. One option, however, would be to exclude the Common Agricultural Policy for the long term, if not permanently, in order to reflect the country’s exceptional circumstances. After all, fisheries and agriculture are likewise excluded from the EEA, without this impairing the functioning of the Single Market. As the EU is pushing ahead with the gradual integration of Ukraine regardless of the accession date, it plans to mobilise significant financial resources, as evidenced by the €90 billion loan for the 2026/2027 period. If Ukraine were to be admitted prematurely – based on its readiness for accession and following a reverse enlargement approach – this could lead to a special status for the country (and possibly other candidates) within the EU.

Gradual integration does not remove the need for EU reform

Concurrent with the accession negotiations, the EU must undertake internal reforms if it is to maintain and strengthen its capacity to act. In the EU’s development, the admission of new members has frequently served as an opportunity or catalyst for reforms of its institutions, its budget, and key policy areas, especially since the 1993 Copenhagen Criteria established the EU’s own capacity to absorb new members as a condition for enlargement. Concerning future accessions, the EU’s heads of state and government, with the “Granada formula” of 2023, underlined not only the Union’s strong geostrategic interest in enlargement. They also stated that reforms should take place both in the candidate countries and within the EU itself as part of the accession process. This formed the basis for the December 2023 decision to formally open accession negotiations with Ukraine. What remained unresolved at the Granada summit, however, was the concrete reform agenda and the timetable.

The primary need for reform within the EU stems from the sheer scale of its expansion, which would have a direct impact on its institutions. With the six Western Balkan states, Ukraine, Moldova, and Iceland, the prospect is of an EU with 35 or more member states, with Ukraine becoming the fifth-largest member state by population.

To maintain the EU’s capacity to act at its current level, reforms would therefore be required across all its core institutions. This would require discussion on a shift to qualified-majority voting in the Council, readjusting the distribution of seats in the European Parliament, and abandoning the principle of “one Commissioner per EU member state”. However, as no large-scale joint enlargement on the model of 2004 is anticipated, the scale of reform must be viewed in relation to the number and size of the new members. If Montenegro were to accede first, the EU would once again comprise 28 members – as it did prior to Brexit. From this viewpoint, there would not yet be an immediate need for institutional reform. The scenario would be different if Ukraine or more than two smaller states were to accede. Gradual integration can thus solve the need for institutional reform only to a limited extent. Even if veto rights were suspended, an EU including Ukraine – or with 30 or more member states – would still require far-reaching governance reforms. Specifically, there would also be a risk that reforms to decision-making structures, which are now being planned for 27 EU member states, would be even more difficult to implement if there were 30 or more member states.

A second area in need of reform arises, by the same logic, from the consequences that potential accessions would have for EU policy areas and, closely linked to this, for the EU budget. Looking at the structure of its budget and the economic profiles of the candidate countries, two policy areas stand out above all: the Common Agricultural Policy and Cohesion Policy, which also remain the two largest items in the EU budget. In the event of a potential northern enlargement, fisheries policy would need to be added to the list.

In these areas in particular, adjustments and long transition periods would therefore be indispensable, not least to ensure that enlargement gains political acceptance in both existing and new member states. This is illustrated by the protests among farmers in Poland and other Central and Eastern European countries against Ukrainian products entering the EU market. Here, too, the question of proportionality arises. Given its size and the structure of its agricultural sector, it is above all Ukraine whose accession would require extensive reforms. For the south-eastern European states, on the other hand, long transitional periods that are gradually phased out are likely to suffice.

The third area requiring reform pertains to the objective of strengthening the safeguards for the rule of law and democracy in a country even beyond its formal accession. Experience with Hungary, Poland, and Slovakia has shown that the development of democratic institutions and the rule of law can be reversed; EU accession does not in itself guarantee that these gains will be maintained and consolidated. So far, the EU’s own safeguard mechanisms have proved inadequate, even though the governments concerned have committed significant breaches of the rule-of-law principles. At the same time, the group of accession candidates consists primarily of states that, despite significant progress made, continue to face major challenges regarding the rule of law, democracy, and anticorruption efforts. These elements are not mere normative ideals; they underpin most EU policies and the functioning of the Single Market. Even under any form of gradual integration, a minimum level of core political criteria must be met. For both the current EU-27 and future members, enlargement should go hand in hand with a strengthening of the rule-of-law conditionality that continues to apply after accession.

A fourth area in need of reform concerns the imperative of advancing the EU as an autonomous security actor. Enlargement in 2004 and 2007 was in each case preceded by the candidate state’s accession to NATO, with the exception of Malta and Cyprus, due to their respective special circumstances. The Western Balkan countries of Albania, Montenegro, and North Macedonia are already members of the Atlantic Alliance. But the potential geostrategic enlargement to include Ukraine and Moldova would also involve two countries that are subject to military attack, under threat, or partially occupied by Russian troops. The prospect of NATO membership is improbable, at least in the medium term.

Nor can the EU offer them adequate security, despite the mutual assistance clause in Article 42(7) TEU and the aim of closing geostrategic grey areas through enlargement. Realistically, only individual European states are in a position to provide security guarantees to Ukraine within the framework of a coalition of the willing, or to assume responsibility in this regard. That said, EU member states should define the mechanism – still entirely open at present – by which the mutual assistance clause is activated and implemented.

Ultimately, even if gradual integration allowed accessions without veto rights, it would neither address the EU’s immediate reform needs nor remove ratification hurdles. Accession treaties must still be adopted unanimously in the Council, approved by a majority of the European Parliament’s members, and then ratified by the national parliaments – as in the case of treaty amendments – in accordance with each member state’s constitutional requirements. In France, for instance, this would require either a three-fifths majority in Parliament or a positive referendum, and Hungary, like all other EU member states, would also have to give its consent.

Interim assessment: New tune, same old song

The impact of Russia’s war against Ukraine on the enlargement process and the EU’s future development objectives cannot be overstated. Although the new tone of enlargement is certainly security-oriented and the orchestra has been supplemented with new instruments, the EU continues to sing the old song that accession remains conditional on meeting the established accession criteria.

New instruments of gradual integration, such as growth plans for the Western Balkans, Ukraine, and Moldova, can – if implemented consistently – accelerate the process while at the same time preventing the criteria from being watered down. Some Western Balkan candidates are undertaking renewed reform efforts in light of the current momentum behind enlargement. Some, however, are banking on the geopolitical landscape trumping the accession criteria, believing that accession can be achieved even without far-reaching reforms. The fact that Serbia, of all countries, hopes to secure a discount on the “fundamentals” in exchange for waiving its veto rights should serve as a warning. Looking at Montenegro, Albania, Moldova, and Ukraine – the four countries the Commission considers to be the frontrunners – neither the structural deficits nor the war-related shortcomings in the rule of law and democracy are likely to be remedied by 2030. Gradual approaches and new safeguard clauses cannot compensate for this. That said, it would also be worth considering whether, beyond Article 7 TEU, an Article 2 TEU-based safeguard clause in the accession treaty could create the possibility of expelling a new member state in the event of serious breaches.

In the context of the Western Balkan countries, it would therefore be prudent for the EU to consistently implement the current methodology – including a strengthened form of gradual integration – to adhere to clear conditionality, and to communicate this unambiguously. In particular, the EU should seize the opportunity to demonstrate, in Montenegro’s case, that full membership can be achieved through the regular process and that adjustment burdens can be managed by means of transition periods. For their part, the member states – in particular Germany as one of the most important partners of candidate countries – should assume greater responsibility for institution- and capacity-building in the candidate countries, which is a prerequisite for participation in the Single Market. Twinning programmes and the EU instrument TAIEX (Technical Assistance and Information Exchange) present ample opportunities in this regard.

A new type of accession association for Ukraine

Ukraine, and linked to it the Republic of Moldova, remain special cases. The EU should now propose a new model for engagement that takes account of the unique circumstances of these two countries. Time is of the essence as the question of accession could be used in Washington and Kyiv as a bargaining chip in negotiations over ending the war, thereby increasing pressure on the EU to act.

The allocation of a special status as an associated accession country would be preferable to a scenario of reverse enlargement. The latter approach would be ill-advised, as it would neither resolve Ukraine’s security concerns nor address the significant challenges of its reconstruction, let alone the difficulties associated with reforms and ratifications within the EU. Instead, a new type of accession association should combine two elements.

First, the EU should fully and consistently commit to the principle of gradual integration prior to accession. To this end, all instruments and formats for closer ties with the EU must be systematically utilised and effectively combined. A key focus should be on participation in the Single Market and investment in Ukraine’s reconstruction. The optimal framework for this, both politically and practically, is an upgraded accession association based on the joint institutions created under the EU-Ukraine Association Agreement (see SWP Comment 42/2024). Whatever scope exists for a demonstrative political upgrade should also be made visible through tangible integration. There are already numerous proposals to this end, ranging from a country’s participation in informal Council meetings following the conclusion of negotiation chapters to observer status in the European Parliament and other institutions, as is already the case in the European Economic and Social Committee.

Second, the offer of an accession association should encompass a substantial security and defence partnership. To this end, every possible opportunity should be leveraged to involve Ukraine in the further development of the CSDP, particularly in programmes to strengthen the defence industry. In doing so, the EU stands to benefit from Ukraine’s experience and industrial base. Willing and capable member states, along with the United Kingdom as a nuclear power, could take the lead and work with Kyiv to establish effective European defence structures closely linked to the EU and to a European pillar of NATO. Such measures should contribute to deliberations on operationalising the mutual assistance clause under Article 42(7) TEU and the implementation of plans for a coalition of the willing in the event of a ceasefire.

An accession association structured in this manner should, on the one hand, provide Ukraine with comprehensive political and economic support and, on the other, leave the country the necessary room for manoeuvre. The prospect of membership thus secured could prove important if a referendum is held in Ukraine on the results of the negotiations to end the war.

Dr Barbara Lippert is Research Director of SWP. Dr Nicolai von Ondarza is Head of the EU / Europe Research Division. Frauke Seebass is a Visiting Fellow at SWP’s Brussels office.