ATHENS, Greece - President Karolos Papoulias called for the leaders of Greece's political parties to meet Sunday in a last-ditch effort to broker a deal for a coalition government and avoid another general election.

Papoulias took the step Saturday when Greece's socialist leader, Evangelos Venizelos, officially gave up the mandate to form a coalition government after three rounds of negotiations proved fruitless.

Papoulias' office announced that the president would meet initially with the heads of the three parties that won the most votes in last Sunday's inconclusive elections - the conservative New Democracy, the Radical Left Coalition (Syriza), and socialist PASOK. He will then meet individually with the leaders of the other four parties that won enough votes for parliamentary seats - the right-wing nationalist Independent Greeks, the Communists, the extreme-right Golden Dawn, and the moderate left Democratic Left.

The format was designed to bring everyone to the table, as Syriza leader Alexis Tsipras had threatened to boycott the talks rather than sit at the same table with Golden Dawn leader Nikos Michaloliakos.

In theory, the president's talks with the party leaders could drag on until the scheduled date for the opening of the new parliament, on Thursday. In practice, precedent shows that talks could take two or three days, George Katrougalos, a professor of constitutional law, told the Associated Press. It is also possible an impasse could be reached Sunday.

If Papoulias fails to broker a coalition agreement, Greece will have to hold new elections next month, most likely on June 10 or 17, prolonging the political uncertainty and bringing Greece's euro membership into question.

Venizelos was the third party leader to try to cobble together a governing coalition after elections last Sunday gave no party enough parliamentary seats to form a government. Voters furious at two years of harsh austerity measures taken in return for international bailouts worth 240 billion euro ($310 billion) rejected Greece's two formerly dominant parties, Venizelos' socialist PASOK and the conservative New Democracy, in favor of smaller parties on the left and right.

The turmoil has alarmed Greece's international creditors, who have stressed that the country must stick to the terms of its rescue deals if it hopes to continue receiving the aid that has kept it afloat since May 2010.

Whether Greece should adhere to the strict austerity measures required for the bailout loans or pull out of the deal has been at the heart of the wrangling over creating a coalition government.

Syriza leader Tsipras, whose party made massive gains to come in second in Sunday's election, campaigned on an anti-bailout platform and insists any new government must cancel the austerity measures. He argues that the terms are so onerous they give the country's battered economy no chance of recovery.

But Venizelos and Antonis Samaras, head of New Democracy, have slammed Tsipras' position as irresponsible. They say his policies would lead to disaster and force Greece out of the European Union's joint currency, which none of the political leaders say they want.