"Creating an independent state of Kosovo on the territory of Serbia, an internationally recognized state, would set a severe precedent," Kostunica said at an economic forum in St. Petersburg.
The leader of Kosovo's provisional government, Agim Ceku, called Friday for world powers to adopt a United Nations resolution cutting Kosovo loose Serbia, reported RIA Novosti, the Russian news agency.
The United Nations thus far has failed to act on the status of the predominantly Albanian province. Russia, a longtime ally of Serbia, has resisted U.N. calls for a vote on Kosovo.
Kosovo, has been under U.N. protection since NATO's bombing campaign against the former Yugoslavia ended a war between Serbian troops and Muslim Albanian separatists in 1999. Kosovo is one of Europe's poorest regions.