Critical talks to form a governing coalition in crisis-struck Greece foundered once more, leading the country one step closer to new elections — and bringing its continued presence in the euro into serious doubt.

Last-ditch efforts by President Karolos Papoulias to broker a deal between wrangling party leaders ended with no deal in sight late Sunday, a week after national elections produced a deadlock, with no party winning enough seats to form a government.

State television said talks would continue Monday evening between the heads of the parties that came in the top three spots in the elections, the conservative New Democracy, radical left-wing Syriza and socialist PASOK, plus the head of the small Democratic Left party, which is in a king-maker position.

But Syriza said it would not attend the talks, state television said, throwing the entire meeting into question.

Syriza head Alexis Tsipras campaigned on a platform for Greece to pull out of its commitments in the international bailout agreement, which has given the country billions in rescue loans. He has insisted he can't back a government that won't overturn the harsh austerity measures taken in return for the bailout.

"Syriza refuses to be a left-wing alibi for a government that will continue the policies the people rejected on May 6," NET state television quoted Tsipras as saying.

Spokesmen for the three other parties said they would attend Monday's meeting.

Power-sharing deal must include left-wing Syriza

Voters furious at the handling of Greece's financial crisis and two years of harsh austerity measures taken in return for billions of euros in international bailout loans punished the formerly dominant socialist PASOK and conservative New Democracy parties in the elections.

The two saw their support crumble to the lowest point in decades, while Radical Left Coalition, or Syriza, made big gains to come in second place after campaigning on an anti-bailout platform.

Spending cuts at issue In return for €240 billion in rescue loans from the European Union and International Monetary Fund, Greece has imposed severe spending cuts, including slashing pensions and salaries in the public sector, and repeated rounds of tax hikes. The austerity has left Greece mired in a fifth year of deep recession, with unemployment spiraling above 21 percent.

New Democracy head Antonis Samaras, PASOK leader Evangelos Venizelos and Democratic Left head Fotis Kouvelis, agree a coalition must be formed that will work to guarantee Greece's continued presence in the euro, but have insisted it must have the participation or at least the support of Syriza.

Tsipras, however, insists he cannot join or even lend his support to a government that will continue implementing the terms of Greece's international bailout.

"The three parties that have agreed on a two-year government in order to apply (the bailout) have 168 seats in parliament," Tsipras said after the meeting.

"Let them go ahead. Their demand that Syriza participate come what may in their own agreement is senseless and unprecedented."

"After today's meeting it is obvious they are demanding that Syriza become an accessory to a crime," Tsipras said earlier, after the discussions with the president.

"In the name of democracy, of our patriotic duty, we cannot accept this shared guilt. We call on all Greeks to condemn once and for all the forces of the past and to realize that only one hope remains: unity against blackmail in order to prevent the continuing barbarity."

If no solution can be found, Greece will have to hold new elections next month, prolonging the political uncertainty and bringing the country's continued membership in the euro into doubt.

The PASOK and New Democracy leaders could form a coalition with Kouvelis's smaller Democratic Left party — combined they would have 168 seats in the 300-member parliament. New Democracy won 18.9 per cent last Sunday while PASOK garnered just 13.2 per cent, compared to nearly 44 per cent in the last elections in 2009. Kouvelis' 6.1 per cent put him in a kingmaker position, with 19 seats.

Tsipras also has his eye on recent opinion polls which show his party would gain strength if Greeks go to the ballot box again next month.

Socialists, conservatives call Syriza's position irresponsible

Venizelos, who spent nine months handling the crisis as finance minister, and conservative leader Antonis Samaras, say that position is irresponsible and will force Greece out of the euro.

Although Sunday's meeting convened by the president with the three top party leaders was inconclusive, Venizelos said that "I retain some limited but existing optimism that a government can be formed."

Samaras appeared more pessimistic.

"I made every effort for the co-operation of all," he said. "Syriza didn't listen to the mandate of the Greek people and does not accept not only the formation of a viable government, but not even the tolerance of a government which would in fact undertake to renegotiate the terms of the (bailout) and the loan agreement."