A group of Kosovo Serbs has demonstrated in the northern city of Mitrovica protesting against Serbia's decision to sign an agreement on closer ties with the European Union.

The protesters burned the U.S. flag and criticized Serbian President Boris Tadic for authorizing the signing of the accord.

Serbian Prime Minister Vojislav Kostunica has opposed signing the accord unless it specifies that Kosovo is an integral part of Serbia. He says an accord without such a provision will constitute support for the February decision by Kosovo's ethnic Albanian majority to declare the area's independence from Serbia   

More than 30 countries, including the United States, have recognized Kosovo independence. But Serbia, backed by its traditional ally Russia, insists on maintaining sovereignty over the area.

EU officials hope the signing of the deal before Serbia's May 11 parliamentary elections will help reformist politicians in the balloting.

The accord, signed Tuesday, specifies that it will not be ratified until Serbia improves its cooperation with international prosecutors seeking to arrest fugitive Serb wartime leader Radovan Karadzic and his top military leader, Ratko Mladic.  Both fugitives from the Balkan conflicts of the 1990s are thought to be hiding in the region.

Kosovo has been under United Nations administration since 1999, after NATO air strikes halted Belgrade's crackdown on ethnic Albanian separatists. 

Some information for this report was provided by AFP, AP and Reuters.