Hard-line Serbian nationalist Tomislav Nikolic is heading for a run-off with pro-western reformer Boris Tadic, according to initial poll results. Numbers so far show Mr. Nikolic receiving nearly one-third of Sunday's vote while his pro-Western rival came in second place.

While elsewhere in former communist Eastern Europe people participated in their first European Parliament elections Sunday, most voters in Serbia tried for the fourth time in 18 months to choose a leader.

According to initial results, nearly one in three voters cast ballots for Tomislav Nikolic of the ultranationalist Serbian Radical Party, whose leader, Voijslav Seselj is on trial at the United Nations Tribunal in The Hague on war crimes charges stemming from the Balkan conflicts of the 1990's.

Mr. Nikolic's main rival, Boris Tadic of the pro-Western Democratic Party, came in second with roughly 28 percent of the vote.

As none of the contenders garnered more than 50 percent of the vote needed for immediate victory, they will now face each other in a final second election round on June 27.

The outcome was a major set-back for the candidate of the ruling reformist government, Dragan Marsicanin and Serbia's wealthiest entrepreneur, millionaire Bogoljub Karic. Both men trailed far behind the main contenders and are now out of the race.

According to news reports, some Western diplomats and analysts fear that if Mr. Nikolic becomes Serbia's next president, he will isolate the republic by bringing down the more pro-Western minority government and scare away foreign investors. In addition, cooperation with The Hague is crucial for future aid from the United States and Europe, which have injected millions of dollars of economic support into the impoverished republic.

But Mr. Nikolic's party has indicated that if he won the election, he would not cooperate in extraditing Serbs to the U.N. war rimes tribunal in The Hague.

He has also vowed that, if elected, he will press for early general elections in an attempt to help his right-wing Radicals carry out these policies.

Some reformist politicians are still hopeful that Mr. Nikolic will be defeated, suggesting late Sunday that voters, in the end, may support Mr. Tadic.

They hope Serbs will recall that Mr. Tadic's Democratic Party spear-headed democratic and economic reforms following President Mr. Slobodon Milosevic's ouster in 2000.