Nationalist candidate Tomislav Nikolic was the leader in Serbia's presidential election on Sunday and will face reformer Boris Tadic in a June 27 runoff, according to a preliminary forecast by independent monitors.

Nikolic, whose Radical Party is led by war crimes suspect Vojislav Seselj, who is now detained by a U.N. war crimes tribunal in The Hague, received about 30.7 percent of the vote, against 27.4 percent for Tadic, according to the independent Center for Free Elections and Democracy.

The figures were based on a partial count from a representative sample of polling stations. Official results were expected by Monday.

If confirmed, the outcome would be a major setback for Prime Minister Vojislav Kostunica, whose ally, Dragan Marsicanin, trailed in fourth place behind upstart candidate Bogoljub Karic, a business leader, according to the projection.

The Serbian election came on the same day that people in other formerly communist nations in Eastern Europe voted for the first time for seats in the European Parliament. The outcome of Serbia's elections could influence the nation's prospects for joining the EU.

Diplomats have warned that a victory by Nikolic in the presidential race would scare off badly needed foreign investors even though he has toned down his nationalist rhetoric and despite the fact that the powers of the presidency are limited.

"I want to make friends in the world for Serbia, not enemies," said Nikolic, 52, as he cast his ballot.

Public opinion surveys published before the election predicted Nikolic would face Tadic in a second round, in which Tadic could pick up votes from supporters of defeated candidates.

Tadic, 46, heads the Democratic Party of the late Prime Minister Zoran Djindjic, who was assassinated last year. Like Nikolic's Radical Party, it is currently in the opposition.

The Radicals oppose handing over suspects to the U.N. tribunal. Compliance with the court is a key condition for closer ties with the European Union.

The party's leader, Seselj, is an old ally of former president Slobodan Milosevic and, like him, is in detention, accused of atrocities in the Balkan wars of the 1990s.

Seselj retains control of the party, which finished first in parliamentary elections in December but failed to take power. Pollsters say the party benefited from disappointment with economic changes enacted since the ouster of Milosevic in 2000.

Serbia has been without an elected president since Milan Milutinovic, also indicted by the war crimes tribunal, stepped down when his term expired in January 2003. Milutinovic subsequently surrendered to the U.N. court.

Three previous attempts to choose a president failed because turnout was less than the required 50 percent of voters. That rule has since been rescinded.

Tomislav Nikolic belongs to a party led by a jailed war crimes suspect.