Brussels – At the start of potential negotiations to end the war in Ukraine, one very general but at the same time key concept is on everyone’s lips: Kyiv needs security guarantees. What these guarantees might actually involve remains unclear, as they were not discussed in detail during the Washington meetings on 18 August. Yet one of them may have wider implications within the European Union: could Ukraine’s EU accession itself serve as a security guarantee?
“On paper, it is a very strong guarantee because of the common defence clause” enshrined in the EU Treaties, says Ondrej Ditrych, senior analyst at the European Union Institute for Security Studies (EUISS), in an interview with The New Union Post. Yet the real risk is that this guarantee remains purely theoretical, as the EU has neither “sufficient” independent defence and deterrence capacity nor contingency plans in place that would make this collective defence “particularly strong against the threat of Russian aggression,” he warns.
Strong, yet not enough
The fact that EU accession is among the potential security guarantees for Ukraine emerges from the discussions in Washington, particularly from an episode first reported by Bloomberg. According to sources familiar with the matter, European leaders—including Commission President Ursula von der Leyen—asked US President Donald Trump to use his influence on Hungarian Prime Minister Viktor Orbán to persuade him to drop his opposition to Ukraine joining the EU.
Trump does not appear to have any particular objection to Kyiv’s EU membership—unlike NATO membership—and during the call with the Hungarian Prime Minister he tried to understand why Orbán is so reluctant to lift his veto on Ukraine’s EU accession talks. There is no public read-out of the conversation, but Orbán’s stance seems unchanged. Following the European Council video conference on 19 August, he wrote on X that “Ukraine’s membership in the European Union provides no security guarantees,” adding that “linking membership with security guarantees is unnecessary and dangerous.”
Although it remains unclear whether Orbán will be swayed by pressure from US President Trump—one of his closest allies—there is no doubt that EU enlargement could be considered at least one of the guarantees on the table in potential peace talks with Russia. Under Article 42.7 of the Treaty on European Union (TEU), the “mutual defence clause” provides that if a Member State is the victim of armed aggression on its territory, the other EU members have “an obligation to aid and assist it by all the means in their power.” This clause is binding, but it does not affect the neutrality of certain Member States and is consistent with the commitments of NATO members.
As EUISS senior analyst Ditrych notes that the mutual defence clause is “rather strong” on paper, but it must be supported by sufficient capabilities and plans to “fill the widening deterrence gap caused by uncertainty about the US’s credible commitment” across Europe in general, and in Ukraine in particular. Even more crucially, EU accession “will take years to complete,” even if the process is unblocked immediately. “Ukraine will need security guarantees sooner if there is to be some freezing of the conflict on terms that are not catastrophic for it,” Ditrych warns.
More than just hypothetical scenarios
Although we are in the realm of hypothetical scenarios—with peace negotiations yet to begin and the very real possibility that Russia will reject all the conditions put forward by the US and Europe—EU enlargement to Ukraine raises some urgent questions and risks.
A key question is what would happen to regions such as Donbas and Crimea, still under Russian military occupation, if negotiations fail—or if Kyiv agrees to a temporary concession without renouncing its legal claim. EUISS senior analyst Ditrych notes that the Cyprus case offers a useful example. While the Republic of Cyprus applied for EU membership for the whole island in 1990, Greek Cypriots rejected a proposed unification plan just before the 2004 enlargement. As a result, only the Republic of Cyprus joined the EU, with Turkish Cypriots in the north of the island still excluded to this day.
Another hypothetical—but far from implausible—risk for the long-term future is what might happen if Ukraine were attacked again by Russia after signing a peace agreement—as occurred after the Minsk agreement—but this time as a full EU member. At present, it is hard to say, as the outcome would depend on several factors. Among them, Ditrych mentions Kyiv’s national defence capacity, the EU’s position at that time, and “the nature of any security guarantees outside the EU framework, including from the US or the UK.”
The state of EU-Ukraine relations
Just four days after the start of Russia’s war of aggression, on 28 February 2022, Ukraine submitted its application for EU membership. On 23 June 2022, the European Council endorsed the European Commission’s recommendation to grant Kyiv candidate status. At the European Council meeting on 14 December 2023, EU leaders gave the green light to open accession negotiations. Following the Council’s approval of the negotiating frameworks, the first intergovernmental conferences were held on 25 June 2024 in Luxembourg.
With the aim of opening the first EU accession negotiation cluster in the first half of 2025, the screening process has been ongoing since last autumn. As recognised by the Council, progress has been made in areas such as the rule of law, judicial and public administration reform—with the renewal of the judiciary being a key focus—alongside efforts to strengthen freedom of expression and media independence, and further enhance the anti-corruption institutional framework.
According to the European Commission, both Ukraine and Moldova “are ready” for Cluster 1 – Fundamentals to be opened. The first group of five negotiating chapters focuses on economic criteria, the functioning of democratic institutions, and public administration reform. Moreover, the Commission has already sent two additional screenings to the Council for Chișinău and Kyiv—on Cluster 2 – ‘Internal Market’ and Cluster 6 – ‘External Relations’. The unanimous approval of all 27 EU member states in the Council is now the only step required.
