Greece's president has so far failed in his last-ditch effort to form a new coalition government for the debt-stricken nation.

President Karolos Papoulias held talks Sunday with the heads of the top three political parties — the conservative New Democracy party, the radically liberal Syriza party and the socialist PASOK party. He was also meeting with heads of smaller parties that won parliamentary seats in the May 6 election.

The talks are the president's final bid to avoid a new election, after the results from the vote earlier this month left no party able to cobble together a majority coalition. PASOK leader Evangelos Venizelos said he had “limited optimism” after Sunday's talks.

The New Democracy and PASOK parties could form a coalition if the small Democratic Left party agrees to link to them, but the party has so far refused to join without Syriza.

Alexis Tsipras, who heads the far-left Syriza party, says he will not join or support a pro-bailout coalition government.

The president has until next Thursday to broker a deal. If he fails, Greece will have to hold a new vote in June.

The key point of contention centers on the Greek government's agreement to demands from its international lenders and European neighbors. They call for sharp austerity measures in exchange for approval of the country's second bailout in two years.

The New Democracy and PASOK parties supported the social spending cuts, but the Syriza party says voters repudiated the austerity agreement. Greeks have frequently taken to the streets in massive, sometimes violent protests against the plan that calls for higher taxes, reduced pensions and elimination of thousands of government jobs.

European leaders have warned the Athens government that it must carry out the austerity measures or they will not send it more bailout money. Financial analysts say that Greece could default on its financial obligations and become the first country to leave the 17-nation euro currency union.