Serbia and Kosovo failed once again to close their differences and clinch a deal to normalise ties in talks brokered by the European Union lasting through Wednesday until Thursday.
"Today has been a very long and intensive day," said EU foreign policy chief Catherine Ashton at the close of daylong negotiations ending after midnight.
"I said last time that agreement was close, that the differences were narrow, but deep. I can say with real confidence today that the differences are narrow and very shallow," Ashton added in a statement.
Saying there were "some hours left" ahead of an EU ministerial meeting in Luxembourg on Monday that will address the situation in the Western Balkans, Ashton hoped both sides "will reflect on whether they can take the final steps necessary to finish this agreement and to move their people forward into the future".
In a surprise move, Ashton called the Brussels talks between Serbian Prime Minister Ivica Dacic and Kosovo counterpart Hashim Thaci in an 11th-hour bid to wrest a deal just two weeks after an EU-brokered dialogue between the Balkans pair broke down despite two years of efforts.
Because of EU red tape, an agreement to ease tensions between the pair is necessary within the coming days if Belgrade is to get the endorsement of a June EU summit to open much hoped-for negotiations to become a member of the bloc.
A report prepared for the summit on the progress achieved by the fractious neighbours in advancing towards European goals and values was to have been released Tuesday but was delayed to give the Wednesday face-to-face a chance.
A refusal by Serbia to strike a deal could indefinitely delay its integration into the EU.
Pristina, which unilaterally declared independence from Belgrade in 2008, is for its part eyeing an association pact with the EU as a reward for normalising ties.
Five EU countries -- Cyprus, Greece, Romania, Slovakia and Spain -- like Belgrade refuse to recognise Kosovo's independence despite its recognition by some 100 nations, including the United States.