Romania has held up a deal for ministers to grant Serbia official EU candidate status.
The decision will now be taken by European Union leaders at this week's summit.
European affairs ministers were to vote to award Serbia candidacy.
However, after objections from Romania they decided instead to "recommend granting Serbia candidate status, and look forward to a decision by the European Council" at the summit on Thursday and Friday.
A draft statement under consideration by the bloc's 27 ministers commended Serbia for its progress in defusing tension with breakaway Kosovo and stated the ministers would "grant Serbia status."
But all EU decisions require unanimity and after Romania objected, a compromise was found after several hours "to recommend granting" and pass on a final verdict to the summit.
Bucharest has demanded guarantees for Serbia's Romanian-speaking minority of Vlachs, some 30,000 people.
"Romania is the only country holding out," said a source close to the negotiations.
