The European Union is edging towards the biggest rethink of its enlargement policy in decades as Russia’s war in Ukraine, fears of institutional paralysis and growing frustration in the Western Balkans force European leaders to confront a question once considered largely theoretical: how to expand the bloc without weakening it.

Officials are debating models that would have been politically taboo only a few years ago — including stripping new member states of veto rights for a probationary period, creating forms of “associate membership” without voting powers, and introducing reversible safeguards to punish democratic backsliding after accession.

For supporters of enlargement, bringing Ukraine, Moldova and the Western Balkans closer to the EU has become a geopolitical imperative in an era of confrontation with Russia and uncertainty over US commitments to European security. But many existing member states remain deeply wary of importing instability, corruption or illiberal politics into a bloc already struggling to make decisions among 27 governments. The result is an increasingly intense argument inside Europe about whether the traditional accession model still works.

“The enlargement of the European Union is a geopolitical necessity,” German Chancellor Friedrich Merz wrote recently in a letter to EU leaders, widely quoted by media in the Western Balkans. But the process, he added, takes “much too long”.

Hungary’s shadow

Part of the discussion is shaped by the EU’s experience with Hungary under former prime minister Viktor Orbán, whose repeated blocking of sanctions, aid packages and foreign policy decisions has fuelled fears among larger member states that admitting more countries without institutional reform could make the bloc ungovernable.

European Commissioner for Enlargement Marta Kos articulated those concerns bluntly earlier this year, before the Hungarian opposition scored a landslide victory in the April general election.

“The EU does not need new Trojan horses,” she said in March. “We need an insurance policy against backward steps.”

According to diplomats and policy papers circulating in Brussels, several member states are now exploring whether future entrants could face temporary restrictions on veto rights, particularly in foreign policy decisions requiring unanimity. The discussions are politically sensitive because EU treaties guarantee equality among member states. But officials increasingly argue that the union can no longer afford to risk paralysis as it contemplates expansion towards 30 or more members.

One proposal under discussion would suspend the right of newly admitted states to block foreign policy decisions during an initial probationary period after accession. The idea has gained traction partly because of concern that Russia or other external powers could exploit internal divisions through sympathetic governments inside the bloc.

“We need stronger safeguards against backsliding on commitments made during the accession negotiations,” Kos said, reiterating a point she previously made in the European Parliament.

Supporters say such mechanisms would be temporary and targeted. Critics warn they risk creating a two-tier Europe in which newer members remain politically subordinate to older ones.

The debate has become particularly acute because Montenegro — currently the most advanced Western Balkan candidate — could theoretically join as early as 2028.

An April report by the Italian Institute for International Political Studies (ISPI), titled "EU Enlargement in Transition: Montenegro at the Frontline", warned that the issue is no longer abstract. “If Ukraine has restored urgency to enlargement,” the report argued, “Montenegro will determine whether the European Union can still turn strategy into action.”

Merz pushes “associate membership”

In his letter to European Council President António Costa, Commission President Ursula von der Leyen and Cypriot President Nikos Christodoulides, whose country currently holds the rotating EU presidency, the German chancellor proposed creating an “associate membership” status for Ukraine.

Under the model, Ukraine would participate in EU institutions and meetings without receiving voting rights, while progressively integrating into EU laws, markets and policies. “While Ukraine should become a full member state,” Merz wrote, “it is obvious that the accession process will not be completed shortly.”

“However,” he continued, “we do not have time for further delays. It is now time to boldly move on with Ukraine’s EU integration through innovative solutions as immediate steps forward.”

According to the proposal, Ukraine could join ministerial meetings and institutional formats while the longer accession process continued in parallel. Merz also suggested the arrangement could include “substantial security guarantees” from EU member states.

The German leader acknowledged the plan would raise “questions regarding political, technical and legal feasibility” but argued it could help anchor Ukraine politically while peace negotiations continued.

The proposal immediately exposed a fundamental dilemma for the EU. Brussels wants to keep Ukraine firmly tied to Europe while avoiding rapid full membership that some member states consider politically or financially impossible. Countries such as Poland and Hungary have raised concerns about the risk Ukraine, with its vast, fertile farmlands, poses to EU agricultural producers, and the overhaul of the Common Agricultural Policy (CAP) that would be required. 

Kyiv, meanwhile, fears becoming trapped in a permanent waiting room, and President Volodymyr Zelenskyy rejected was quick to reject Merz’ proposal proposal.

“It would be unfair for Ukraine to be present in the European Union, but remain voiceless,” Zelenskyy wrote in a letter to EU leaders, according to Reuters. “The time is right to move forward with Ukraine’s membership in a full and meaningful way.”

For Ukraine, the concern is not merely symbolic. Kyiv worries that “associate membership” could become a substitute for full accession rather than a stepping stone towards it, particularly if political enthusiasm for enlargement fades in Western Europe after the war.

Ukraine formally applied for EU membership days after Russia’s full-scale invasion in February 2022. It received candidate status later that year, and accession negotiations formally opened in June 2024. But despite strong rhetorical support from Brussels, diplomats privately acknowledge that membership before the end of the decade would require political shortcuts unprecedented in EU history.

A continent divided

Behind the institutional debate lies a deeper divide about Europe’s future. France, the Netherlands and some other member states remain wary of rapid expansion before the EU reforms its own decision-making structures and budget system. Many governments fear enlargement could dilute the Union’s capacity to act at precisely the moment Europe faces mounting security threats and economic competition from China and the US.

A policy paper published in April by the German Institute for International and Security Affairs (SWP) argued that the EU’s “capacity to act” remains one of the central unresolved questions of enlargement.

“The realisation of the ideal that a larger EU will also be a stronger one,” the paper said, “is contingent upon the successful navigation of two significant challenges.” Those challenges include both weaknesses within candidate countries and the EU’s own inability to reform.

“At the centre,” the report noted, are unresolved disputes over fiscal policy, the Common Agricultural Policy, cohesion funding and foreign policy decision-making rules.

The report argued that Ukraine represented “a special case” requiring innovative political solutions, while the Western Balkans should remain largely within the traditional accession framework. “As a preliminary step towards membership,” the authors wrote, “the EU should offer Kyiv a new type of accession association that also includes a security and defence dimension.”

Separately, the European Council on Foreign Relations (ECFR) recently proposed a model called “Political Accession with Commitments to Transformation”, or PACT.

Under the proposal, countries such as Ukraine would immediately receive political membership and security guarantees — including participation in parts of EU decision-making and the application of the EU’s mutual defence clause — while access to funding and broader voting rights would be phased in gradually depending on reforms.

“Compared to the fast-track model, which actually delays entry until all reforms are completed, PACT grants immediate political membership,” the ECFR argued. The model would also include a “reversibility mechanism” allowing Brussels to suspend rights or funding if democratic backsliding occurred.

The Balkans grow impatient

The Western Balkans, meanwhile, are watching the debate with a mixture of frustration and alarm. Countries in the region have spent years — in some cases decades — waiting for accession to advance, only to encounter repeated delays, vetoes and shifting political criteria.

That stagnation has fuelled disillusionment with the EU and opened space for Russian, Chinese and Turkish influence across parts of the region, as shown this week by Serbian President Aleksandar Vucic's comments on arrival in Beijing, when he slammed EU pressure over Belgrade's foreign policy. 

This is likely more a sign of frustration over the sluggish pace of accession than a sign Serbia plans to abandon its accession efforts. Similar frustration has been expressed in Tirana and Skopje, the latter because of the repeated roadblocks to North Macedonia's accession process due to bilateral disputes with its EU member neighbours. 

In February, Vucic and Albanian Prime Minister Edi Rama jointly proposed a model of “phased accession” in an article published by Frankfurter Allgemeine Zeitung. Under their proposal, candidate states would gain access to the EU single market and Schengen free-travel area before full political membership. The arrangement would not include veto powers, European commissioners or representation in the European Parliament.

“People need to see that the process is credible and that membership is attainable within a reasonable timeframe,” Vucic and Rama wrote. They argued that accelerated economic integration could “strengthen the EU’s economic and political position” while easing fears among skeptical member states about institutional disruption.

However, the initiative received a cool reception in Brussels, where Kos dismissed the proposal publicly. “I am unsure if the leaders know how much you have to deliver if you want to be a part of Schengen or common market,” she said as quoted by Politico, adding that reforms required for economic integration were as demanding as those required for EU membership itself.

Yet some Balkan leaders appear increasingly willing to accept compromises. Rama said this month that Albania would support temporary limits on veto rights if it helped speed accession. “We will not waver, whatever it takes to get in,” he said.

Describing Albania jokingly as “the EU Taliban”, Rama said enlargement required “creative” and “innovative” solutions because “Europe has a war to deal with on its own soil”, Euractiv reported. “I support it,” he said of proposals to curb veto powers temporarily for new members.

Rama also criticised the EU for moving too slowly. “It’s a big, big bet to wait,” he said of delays affecting Moldova’s accession process. “It’s not going to happen like this — it cannot happen like this.”

Enlargement as security policy

For many European officials, enlargement is no longer primarily about economics or democratic transformation, it is increasingly viewed as hard security policy. The European Parliament adopted a report in March calling enlargement “a strategic response to the evolving geopolitical reality and a vital investment in the EU’s security and stability”. The report argued that the “cost of non-enlargement” could exceed the costs of expansion itself by creating geopolitical “grey zones vulnerable to antagonistic foreign influence”.

That logic has become especially powerful since Russia’s invasion of Ukraine. European governments increasingly see the prospect of EU membership as a way to stabilise vulnerable states, reduce Russian influence and consolidate Europe’s eastern frontier. However, despite the geopolitical rationale, it is still difficult to reconcile with the EU’s traditional insistence on a slow, rules-based accession process. Some officials now openly acknowledge that enlargement may ultimately depend less on technical criteria than on political decisions by major capitals.

“Brussels now realises it will be impossible to integrate Ukraine and the Western Balkans without a political decision and compass from member states,” the ISPI report concluded.

For now, the EU is caught between two dangers: that moving too quickly could destabilise the union from within, and that moving too slowly could weaken Europe strategically at a moment of profound geopolitical upheaval.