The European Commission has backed the opening of formal membership talks with Albania and Macedonia as the EU looks to expand into the Balkans and grow for the first time in years.

The announcement comes a month ahead of a key summit in Sofia when the leaders of six Balkan nations will be given fresh hope that some could become members by 2025.

EU diplomatic chief Federica Mogherini said the commission, the executive arm of the EU, recommended that member states "open accession negotiations with Albania and with the former Yugoslav Republic of Macedonia".

But she stressed that any prospective members must make sweeping reforms to secure their entry to the club, which currently counts 28 countries as members, although Britain is set to leave next year.

European Commission President Jean-Claude Juncker put all enlargement on hold four years ago and the Balkan states have become increasingly impatient.

Montenegro and Serbia are the front runners to join, having already started the formal membership process, with Albania, Bosnia, Kosovo and Macedonia lagging behind.

In February, the EU announced its new strategy for the region, which aims to give membership to some states by 2025 but insists they must first resolve all border rows.

These include a bitter and long-running dispute between Macedonia and EU-member Greece over its name, which Athens insists refers to its own northern province.

Ms Mogherini told reporters at the European parliament that Montenegro and Serbia have "progressed well" with their reforms, adding that "maintaining and deepening the current reforms must continue in all areas".

These areas are the rule of law, human rights, democratic institutions and public administration, as well as ensuring economic competitiveness.

Bulgaria, which currently holds the EU's rotating presidency, has warned it is now or never for expanding the European Union into the Balkans as concerns grow about Russia's influence in the EU's eastern backyard.