Serbia's pro-Western President Boris Tadic won re-election on Sunday against nationalist challenger Tomislav Nikolic in a vote that will determine the country's future ties with the European Union.

The election commission said it was a narrow victory for Tadic, with a projected 51 percent of the vote.

The election was seen as a referendum on how Serbia should deal with the West after the imminent loss of the breakaway province of Kosovo. Tadic says European Union membership must remain Serbia's priority whatever happens. Nikolic advocates turning to Russia instead of the West.

"Tadic won, my congratulations," Nikolic said at his party headquarters. "I would like to call on everyone to stay calm."

Monitors put turnout at about 67 percent, compared with 61 percent in the first round two weeks ago. This would be the highest turnout since the 2000 election that ousted Slobodan Milosevic after more than a decade in power.

Political analysts had said only a strong turnout could counter the dedicated voters of Nikolic, who beat Tadic by 40 percent to 35.4 percent on Jan 20, in a field of nine candidates.

Both oppose Kosovo's independence drive. Nikolic wants Serbia to turn to Russia to punish the West for backing Kosovo's majority Albanians. Tadic is asking Serbs to swallow their pride and pursue EU membership.

Kosovo's 90-percent Albanian majority was looking to set a date for a declaration of independence after Sunday's result.

Political sources say that if Tadic is confirmed as the winner, they will wait a few weeks in accordance with the wishes of the EU. If Nikolic had won, a declaration could have been made as early as next weekend.

The province, Serbia's medieval heartland, has been run by the United Nations since NATO drove out Serb forces in 1999 to halt ethnic cleansing during a counter-insurgency war.

A Nikolic victory could have ended the fragile coalition of Tadic and nationalist Prime Minister Vojislav Kostunica.

Kostunica has made the defense of Serb sovereignty over Kosovo the keystone of his policy. He has attacked an EU plan to send an 1,800-strong mission to supervise the transition to U.N. rule as a prelude to recognizing the new state.

This week he said he could not support Tadic's re-election bid because his coalition ally had refused to commit himself to pledging that Serbia would refuse a deal with the EU if the bloc went ahead and supported Kosovo's independence.

Neither the EU nor the United States has shown any sign of backing down over Kosovo's independence, despite warnings from Russian President Vladimir Putin that he will never accept it.