By Justyna Pawlak and Fatos Bytyci
BRUSSELS/PRISTINA (Reuters) - The European Union gave Serbia a last chance to clinch membership talks with the bloc on Tuesday, summoning the Balkan country to new negotiations on ending the ethnic partition of its former Kosovo province.
With speculation rising that a deal might be near, diplomats said the European Commission, the EU's executive arm, would delay a report on Serbia's readiness to start accession talks.
The report had been due on Tuesday, before the European Council considers its findings on April 22.
EU foreign policy chief Catherine Ashton, who two weeks ago declared EU-mediated talks between Kosovo and Serbia over, said she had invited the prime ministers of both sides back to Brussels on Wednesday.
Serbia, which says it will never recognize Kosovo as a sovereign state, last week rejected the principles of an agreement that emerged through six months of talks led by Ashton.
"I have asked them to come in a constructive spirit, ready to explore different options and agree to a mutual compromise," Ashton said in a statement.
Kosovo's EU integration minister, Vlora Citaku, tweeted: "Kosovo and Serbian delegations to meet tomorrow again in Brussels! Lets hope this opportunity won't be missed!"
Five years since Kosovo seceded, Serbia has signaled it is ready to come to terms with the loss of the majority-Albanian territory - to Serbs the cradle of their Orthodox Christian faith - in exchange for the economic boost of closer ties with the EU.
Accession talks would help unlock Serbia's potential as the largest market in the former Yugoslavia, providing a stimulus for reform and a signal of stability for much-needed foreign investors. The country will watch neighboring Croatia, its wartime foe, become the EU's 28th member on July 1.
Kosovo broke away from Serbia 1998-99, when NATO waged an 11-week air war to halt the killing and expulsion of ethnic Albanian civilians by Serbian forces trying to crush a guerrilla insurgency.
It was late Serb strongman Slobodan Milosevic's last throw of the dice in the bloody collapse of federal Yugoslavia before his ousting in 2000. Kosovo declared independence in 2008 and is recognized by more than 90 countries, including the United States and 22 of the EU's 27 members.
Serbia retained de facto control over a small, Serb-populated pocket of north Kosovo, in an ethnic partition that frequently flares into violence and that the EU says must end. The standoff has frustrated plans by NATO to further cut back its Kosovo peace force, which now numbers 6,000 soldiers.
In a major U-turn in official policy, Serbia's ruling coalition has offered to recognize the authority of Pristina over the north, but wants autonomy for some 50,000 Serbs living there.
Talks in Brussels had foundered over the powers Serbs would wield, particularly over policing and courts. Serbian government officials said progress had been made over several days of informal contacts with Pristina.
There was no official confirmation from Belgrade that Serbian Prime Minister Ivica Dacic, on a visit to Lithuania on Tuesday, would attend the talks on Wednesday.
"We'll announce our official position as soon as we have word from the prime minister," a Serbian government official told Reuters on condition of anonymity.
Even if the EU opens accession talks, Serbia is unlikely to join before at least 2020. Fellow former Yugoslav republic Slovenia joined in 2004. Croatia follows in July and Montenegro has begun membership talks. Macedonia is a candidate for membership, Bosnia has yet to apply and Kosovo is last in the queue.
In a report on Macedonia, EU enlargement commissioner Stefan Fule said progress had been made despite a spike in political tensions and reported "new momentum" in efforts to resolve a long-running row with Greece over Macedonia's name, which is holding up its integration with the EU and NATO.
(Additional reporting by Aleksandar Vasovic in Belgrade and Adrian Croft in Brussels; Writing by Matt Robinson; Editing by Alison Williams)