Stunned by the triumph of the extremist Serbian Radical party led by the war crimes indictee Vojislav Seselj in Sunday's election, Vojislav Kostunica, the former Yugoslav president whose party came second, faced the need to rebuild bridges with his democratic rivals to head a coalition and become prime minister.

Mr Kostunica did not help matters by denouncing the outgoing reformist Democratic party government and blaming its record for the extremists' gains. Without the Democratic party in a coalition Mr Kostunica's party, which won 53 seats, cannot muster a majority.

Boris Tadic, the outgoing defence minister and leader of the Democratic party - which took 37 seats - offered an olive branch to Mr Kostunica.

"It is important that democratic groups now form a bloc that will ensure that Serbia remains on the path of democratic reforms," he said.

With the G17 Plus group winning 34 seats, the three main reformist parties that overthrew Slobodan Milosevic three years ago took 42% of the vote and a total of 124 seats, but remain two short of a majority.

While the extremist Radicals, who ran a militia engaged in ethnic cleansing during the Croatian and Bosnian wars of the 90s, took 81 of the 250 seats they too look unable to build a governing majority, despite Mr Milosevic's Socialists, a likely partner, winning 22.

The fifth-placed monarchist Serbian Renewal Movement of Vuk Draskovic took 23 seats and its expected participation in a Kostunica-led coalition would ensure a majority.

For that to work, Mr Kostunica still needs to cooperate with the Democratic party of Mr Tadic. They broke amid bitter recrimination last year and Mr Kostunica has ruled out a coalition.

The complicated electoral arithmetic portended a protracted period of horsetrading likely to reinforce the popular perception that the reformers are corrupt, preoccupied with their personal positions, and incapable of ruling effectively.

It was such perceptions after two years of bickering that helped the extreme nationalists to Sunday's triumph.

That shock also sent a chastening signal to Washington and Brussels, which have invested heavily in the reformers in an attempt to erase extreme Serbian nationalism.

Javier Solana, the EU's foreign policy chief who has made the Balkans one of his foreign policy priorities and may now be pondering where he has gone wrong, urged Mr Kostunica and his rivals to bridge their differences.

"I appeal to all democratic forces to work together to ensure that a new government based on a clear and strong European reform agenda can be formed rapidly," he said. Brussels would lend its "full support to such a government".