July 27, 2006 11:51 AM

BELGRADE, Serbia-Serbia's ultranationalists warned Thursday that they will "fight for Kosovo" in case the contested province gains independence at ongoing U.N.-brokered talks.

Tomislav Nikolic, the leader of the increasingly popular Serbian Radical Party, said that no leader in Serbia will accept Kosovo's independence.

"The whole world must know that," Nikolic declared. "Serbia will fight for Kosovo." He did not elaborate.

Serbian and ethnic Albanian officials were not immediately available for comment.

Kosovo is formally part of Serbia, but the province has been run by the United Nations since a 1999 NATO air war forced Belgrade to stop attacks against ethnic Albanian separatists and pull out of the region.

The talks to decide Kosovo's future status started early this year. Most analysts have predicted that Kosovo might gain some form of independence, despite Serbia's opposition.

Nikolic acknowledged that "if they want to take away Kosovo ... from us," Belgrade cannot prevent that. He added that "Serbia will be peaceful and stable as long as the talks are going on," but could explode in unrest in case of Kosovo independence.

Serbia's President Boris Tadic and Prime Minister Vojislav Kostunica took part early this week in a face-to-face meeting with ethnic Albanian leaders in Vienna, Austria, as part of U.N.-brokered negotiations.

Both face a mounting challenge from the Radicals, who ruled together with late ex-nationalist leader, Slobodan Milosevic, in the next election in Serbia in 2007.

Also this week, the U.S. envoy for Kosovo talks, Frank Wisner, urged both Serbia and the ethnic Albanians to be more flexible and work together to find a compromise on Kosovo.