Greek PM Lucas Papademos summoned political allies to an emergency meeting on Sunday after hours of "superhuman" negotiations with EU-IMF bailout auditors failed to produce a rescue deal.
An accord has to emerge Sunday for Greece to avert a disorderly default in March, Finance Minister Evangelos Venizelos warned ahead of the meeting scheduled tentatively for 1300 GMT.
And Eurogroup chief Jean-Claude Juncker piled further pressure on Athens, threatening to cut off funds if reforms were seen to stall.
"If we were to see that everything was failing in Greece then there wouldn't be a new (refinance) programme," Juncker told German magazine Spiegel.
"Everything must be concluded by (Sunday) night... so that we can be within the timetable given the bond maturities in March," Venizelos said.
"We are on a knife edge," the minister warned.
Athens has been in talks with the European Union, the International Monetary Fund and the European Central Bank -- known as the 'trioka' here -- on further action needed to unlock a new eurozone rescue deal worth 130 billion euros ($171 billion) pending since October.
A further round of negotiations with the public lenders will begin at 1100 GMT, Papademos' office said.
Pressure is also mounting for an agreement with private lenders to wipe out part of the 350-billion-euro Greek debt, as Athens faces loan repayments of 14.4 billion euros ($19 billion) on March 20.
A senior government official on Sunday said "superhuman" negotiations with auditors from the troika had made progress but that certain gaps remained.
Chief among them is the public creditors' demand for labour cost cuts, rejected by unions and by the three-party coalition backing Papademos' government.
Opponents argue that further reductions will exacerbate a recession already fueled by two years of austerity measures.
"Agreement by the political leaders is necessary," the official said.
George Karatzaferis, whose far-right party LAOS is one of the coalition's three partners, on Saturday threatened to reject the eurozone bailout deal.
"I do not function well under conditions of blackmail," Karatzaferis told a party gathering in the northern city of Thessaloniki.
"If the package is not to our liking, we will not accept it," he said.
Papademos has reportedly threatened to resign if his coalition backers reject the demanded austerity measures, but government spokesman Pantelis Kapsis refused to confirm this.
Coalition leaders are strongly opposed to further civil service cuts, now reportedly affecting teachers and military staff, and for a reduction in the minimum monthly wage which now stands at 750 euros.
Europe's commissioner for maritime affairs Maria Damanaki, who is Greek, on Sunday said the country has followed a "disastrous path" until now.
"For two years we have promised changes which we failed to pursue, or failed to complete," she told To Vima weekly.
"We say much and do little. We agree to timetables we do not keep. Hence we have created the image of a state that is systematically unreliable," Damanaki said.