Serbia's Minister of Energy and about 20 other Serbs walked out of a regional ministerial conference in Athens today because an ethnic Albanian from the breakaway province of Kosovo was taking part.
In a foretaste of the diplomatic freeze Serbia is likely to impose if Kosovo wins independence against its will, Aleksandar Popovic left the conference abruptly when the chairman refused to prevent Kosovo's representative from speaking.
"I considered it was my obligation to leave the conference," Mr Popovic told Beta news agency.
"At the same time, without any previous agreement, the representatives of all Serbian institutions and companies present left as well."
Leaders of Serbia and the Kosovo Albanians sat down on Friday for face-to-face talks at the United Nations in New York to seek compromise between Kosovo's demand for independence and Serbia's insistence on its sovereignty.
The province has been run for the past eight years by the United Nations, after Nato drove out Serb forces in 1999 to end a counter-insurgency war in which thousands of Albanian civilians were killed and 800,000 expelled.