Serbia and Montenegro could join the EU in 2025, the European commission has said, as Brussels seeks to renew the path to membership for six western Balkan states after years of distracting economic crises and enlargement fatigue.

“The future of the union is not bound to be at 27,” said the EU’s foreign policy chief, Federica Mogherini, referring to the number of countries that will be in the EU once Britain leaves in 2019. The 2025 goal was “not a target date, not a deadline”, she said, stressing that countries would only be able to join through merit-based processes that meant strengthening the rule of law and tackling organised crime and corruption.



Among the six western Balkan countries in the EU waiting room, only Serbia and Montenegro have started membership talks, but Mogherini said the rest could still catch up. Albania and Macedonia are deemed to be making significant progress, while Bosnia-Herzegovina and Kosovo are further behind.



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Jean-Claude Juncker, the European commission president, who ruled out any further EU enlargement at the start of his term in 2014, said the 2025 date was intended as “encouragement so the parties concerned work hard”. He said countries would not be allowed to join until border disputes were resolved. “This game of saying that this problem will be kicked into the long grass, after accession. I won’t accept it,” he said.

The EU has learned the hard way that long-running political disputes are harder to settle once countries are inside the bloc. Unsolved problems include the Slovenia-Croatia border dispute and the divided island of Cyprus.



In a western Balkans strategy paper published on Tuesday, the commission also announced it wanted “a more effective system … to tackle systemic threats to or breaches of the rule of law in any EU member state”.

The EU executive in Brussels has been engaged in a two-year standoff with Poland over changes to its judiciary, but critics say the process is cumbersome and has had little influence on the Polish government so far.



The strategy reflects the EU’s renewed attention to the region, as Russia and Turkey increase their influence, amid concerns about backsliding on democracy.



The UK’s departure from the EU means Balkan states will lose one of their strongest advocates, although Britain will host a summit on the western Balkans in July 2018. Some EU officials have raised eyebrows at the UK’s attempts to remain at the forefront of European integration in the Balkans.

The London summit follows an EU-Balkans summit in Bulgaria, which holds the EU’s rotating presidency. “The United Kingdom is leaving the European Union so the EU’s work on the western Balkans will be mainly done by the Bulgarian presidency,” one EU official said.