Serbia's incumbent president, Boris Tadic, finished first in his bid for re-election, but fell far short of a majority, so a runoff vote will be held in two weeks.

Mr. Tadic and his main challenger, Tomislav Nikolic of the nationalist Serbian Progressive Party, finished first and second Sunday in a field of 12 candidates. Together they won more than half of nearly four million ballots that were cast, and Serbia's Election Commission said Mr. Tadic has a 13,100-vote lead over Mr. Nikolic.

In voting for parliament, Mr. Nikolic's nationalists won 73 seats, ahead of Mr. Tadic's Democratic Party bloc, which won 67 seats. Since Serbia's opposition socialists won 44 seats, the party once led by Slobodan Milosevic appears to hold the balance of power in talks on forming a new government.

In Washington, the White House congratulated Serbia on holding a successful election. A spokesman says the United States looks forward to working with Serbia's political leadership as it moves toward EU membership, no matter which party leads the next government.