Greece's president will meet the leaders of the country's three biggest parties on Sunday in a last-ditch attempt to cobble together a coalition and avoid a repeat election in a few weeks.
Evangelos Venizelos, the head of the socialist PASOK party, officially gave up the mandate to form a coalition government on Saturday, the third party leader to fail following negotiations with other parties.
President Karolos Papoulias' meeting with conservative leader Antonis Samaras, Venizelos and Alexis Tsipras, the leader of Syriza, a leftist coalition, will take place at 09:00 GMT on Sunday, a statement from the president's office said.
If the talks fail, new elections will have to be called for next month, prolonging the political uncertainty and bringing Greece's euro membership into question.
Venizelos was the third party leader to try to bring 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 $310bn rejected Greece's two formerly dominant parties, PASOK and the conservative New Democracy, in favour 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 funds that have been keeping 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.
Tsipras' Syriza, which made massive gains to come second in Sunday's election, campaigned on an anti-bailout platform and insists any new government must cancel the austerity measures.
He argues the terms are so onerous that they are giving the country's battered economy no chance of recovery. But both Venizelos and Samaras 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, something that none of the political leaders say they want.
New elections likely
"The prospects of [the president] succeeding [in forming a coalition], in the opinion of many observers and analysts here, are not really optimistic," Al Jazeera's Tim Friend reported from Athens on Saturday.
"The differences between the three main parties is so large, or at least between the bulk of them and one of them - the radical left. So I don't think that bridge can be built, it's a step too far. I think we are probably going to have elections here in the middle of June."
Hopes had been raised that a solution could be found in the form of a partnership between New Democracy, PASOK and the smaller Democratic Left party of Fotis Kouvelis, whose 19 seats put it in a potential kingmaker position.
But all three parties have insisted they cannot join forces without the support of Syriza, given its strong performance in the elections.
Handing back the mandate to the president, Venizelos said that while there had been a meeting of minds between his party, Democratic Left and New Democracy, Tsipras was sticking to his position.
Papoulias could break the deadlock when he calls the party leaders for a last-ditch attempt at a solution, but chances are slim. Recent opinion polls show Syriza would win new elections if they are called.
Although it would not get enough votes to form a government on its own, it would benefit from regulations that give the first party a bonus 50 seats in the 300-member parliament, putting it in the dominant position to seek coalition partners among other anti-bailout parties.
But all one would likely get from a second round of elections is at best a reversal of the two lead positions, our correspondent said.
"The radical left may well get the most votes, but not an absolute majority, and the mainstream conservatives would come second," Friend said.
"Effectively they would be left back in the position where they are now, where they would have to start talking about agreements. So even then, the election may not achieve any conclusive result."