Brussels (AFP) - The EU on Tuesday backed the opening of formal membership talks with Albania and Macedonia as the bloc looks to expand into the Balkans and grow for the first time in years.

The announcement comes a month ahead of a summit in Sofia when the leaders of six Balkan nations will be given fresh hope of eventually joining the EU, amid rivalry between Brussels and Moscow over the region.

Skopje and Tirana both welcomed the move and vowed to work hard to remove obstacles on the long way to full membership.

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

Mogherini 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 Balkans states have become increasingly impatient.

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

In February the EU unveiled 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.

The EU has been wary of admitting new members before they settle their differences. The border rows will be a particular point of contention in a region still bedevilled by the aftermath of the bloody break-up of Yugoslavia in the 1990s.

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.

- 'Drift to Russia' -

Macedonian Prime Minister Zoran Zaev, whose country's NATO membership bid has also been held up by the row, said his government wanted to resolve the dispute as soon as possible.

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"We are making efforts to finish this before the summit... but we would be even happier if it can happen earlier," Zaev told a press conference in Skopje.

Albanian Prime Minister Edi Rama said the former communist country has "passed the historic test of our rapprochment with Europe" but acknowledged hard work lay ahead.

Rama told reporters in the capital Tirana that it marked "the opening of a new, more difficult phase of reforms and reinforcing the fight against crime and corruption."

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.

An ally of Russia, Serbia has refused to recognise its former breakaway province of Kosovo since it declared independence a decade ago. Five EU countries also do not recognise its independence.

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 Moscow's influence in the bloc's eastern backyard.

French President Emmanuel Macron underscored the concerns, saying: "Yes to anchoring them in the EU and not letting them drift toward Turkey and Russia."

But Macron insisted on reforming the bloc before admitting them, saying: "I will not defend any new enlargement until there is a deepening and improvement of our own Europe."