The hardline Serbian Radical Party (SRS) under Vojislav Seselj, who is awaiting trial on war crimes charges at the UN tribunal in The Hague, offered on Monday to join forces with the Democratic Party of Serbia (DSS) under former Yugoslav president Vojislav Kostunica.
"There are obviously many common points in our two programmes which could make us form a government together," SRS deputy leader Tomislav Nikolic told reporters a day after the nationalists won the largest share of votes.
"We are suggesting to the DSS to listen to the will of its voters. It is obvious that only the SRS and the DSS can form the government," Nikolic said.
The Radicals will be the biggest party in the new parliament after winning 27.5% of the vote on Sunday, according to partial unofficial results. The election outcome sparked concern across Europe of a return to nationalism in the former Yugoslav republic.
Together with the Socialist Party of former Yugoslav president Slobodan Milosevic, who has been on trial at the war crimes court since February 2002, they could command more than a third of the vote.
Both Seselj and Milosevic are facing war crimes charges for their roles in the Balkan wars that tore apart former Yugoslavia in the 1990s.
Kostunica, who helped overthrow Milosevic in 2000, but then opposed his extradition to the UN tribunal, has repeatedly ruled out joining forces with the Radicals despite his reputation as a "soft nationalist."
Democrat leader Kostunica (C)
says too early to talk coalition
He has been consistent in his opposition to the hardline nationalism embodied by the likes of Seselj, who wants to role back reforms designed to bring Serbia into the European Union and NATO.
"It is too early to talk about combinations for the majority government. The decision about the coalitions will be made by the main board of the party," Kostunica said early on Monday as the election results trickled in.
"I have presented certain criteria before the elections, and this will have a positive impact on the board's decision."
The European Union expressed hope on Monday that Serbia would stay on course for reforms necessary to join the bloc.
"I appeal to all democratic forces to work together in order to ensure that a new goverment based on a clear and strong European reform agenda can be formed rapidly," said EU foreign policy chief Javier Solana.
"The EU will give its full support to such a government," he said.
"The EU will give its full support to such a government"
EU foreign policy chief
No major political groups have said they will side with the nationalists, and analysts still expect a democratic bloc of four parties, led by the DSS, to pull together in a potentially unsteady majority.
But analysts have said the prospect of further political instability could delay reforms which are required for Serbia's entry into the Euro-Atlantic clubs and further complicate relations with the UN court in The Hague.
Neither Milosevic nor Seselj can take their seats in parliament because they are in UN custody, but European diplomats there said their election had a powerful symbolic impact.
"This will be seen as negative because of the symbolic value that these two people represent," Maurizio Massari, the Organisation for Security and Cooperation in Europe ambassador to Serbia and Montenegro, told AFP.
"The reaction will be negative from the emotional point of view but to be honest, in terms of the real impact on Serbian political life, it will be irrelevant."
With the Orthodox Christmas celebrations coming up, a new government is not expected to be in place for weeks.
But diplomats said the new administration would have to move fast on issues such as the extradition of suspected war criminals to win the confidence of the international community.