Embattled Prime Minister George Papandreou was to hold emergency meetings of his cabinet and socialist party lawmakers as calls mounted for the creation of a national unity or a transitional government to safeguard the rescue deal.
His government was also set to lose its parliamentary majority in a confidence vote due Friday, further adding to the political turmoil over Papandreou's shock referendum plan announced this week.
Finance Minister Evangelos Venizelos -- a former challenger for the Pasok party leadership -- came out strongly against the referendum, warning it could scupper the hard-won 100 billion euro bailout.
"Greece's place in the euro is an historical conquest by the Greek people that cannot be placed in question... this cannot be made dependent on a referendum," Venizelos said after returning from G20 talks in Cannes.
Papandreou was summoned to Cannes Wednesday by furious eurozone leaders concerned that the deal hammered out last week to slash Greece's debt by almost a third would be dealt a death blow by the referendum.
European leaders warned that if Greece does not respect the terms of the rescue deal, it will not get "one more cent" from the next planned installment of EU and IMF funds.
And the European Commission said that under EU treaties it would be impossible for a member state to exit the euro without also leaving the European Union.
The eurozone crisis is at the top of the agenda of the G20 summit which opened in Cannes Thursday.
The conservative leader of Greece's main opposition Antonis Samaras, whose party has 85 seats in the 300-member parliament, called for a transition government to keep the debt deal afloat and to call snap elections.
"I ask for the formation of a temporary transition government with the exclusive responsibility to immediately hold elections, and ratify the loan deal under the present parliament," Samaras said in a televised address.
It marked an abrupt about-face by Samaras who has consistently opposed the loan agreements negotiated by the Greek government with its creditors -- the EU, IMF and European Central Bank -- on the grounds that they stifled growth and worsened recession.
But on Thursday he said: "The new loan deal is inevitable and must be secured."
In a further possible sign of discontent with Papandreou, three possible successors to the prime minister held private talks ahead of the crisis cabinet meeting, the semi-state Athens News Agency reported.
Health Minister Andreas Loverdos, Education Minister Anna Diamantopoulou and Infrastructure Minister Yiannis Ragoussis are are all opposed to the referendum and have called for the creation of a national unity government.
The three ministers last month penned a joint article calling on the government to stick to its controversial economic reforms.
"At this very difficult moment, the priorities are clear," Diamantopoulou told reporters.
"We must remain in the euro, sign this particularly successful (EU) deal... above all, however, we have the responsibility to maintain unity among the Greek people."
The premier, facing mounting social opposition to his austerity policies, called for a referendum and a confidence vote to allow him to avoid early elections.
But the gambit ran into fierce opposition both at home and abroad and sent stock markets tumbling.
In Cannes, Papandreou said the referendum could be held as early as December 4.
But his parliamentary majority was evaporating, with two socialist deputies threatening to withhold support over the referendum, which would give Pasok 150 votes in the 300-seat chamber.
However, the government could still win Friday's vote, depending on the numbers who take part.
Despite the uncertainty, Greek stocks jumped 3.82 percent.
In Cannes, German Chancellor Angela Merkel and French President Nicolas Sarkozy said Wednesday they hoped Greece would stay on board, but warned Athens would not get a free ride.
"The Europeans and the IMF can't release the sixth tranche of loans to Greece until Greece endorses the package of October 27," Sarkozy said, calling for the referendum "if one is needed" to be carried out swiftly.
Eurozone chairman Jean-Claude Juncker said the currency union hoped to keep Greece as a member "but not at any price".
IMF chief Christine Lagarde also warned she would not move on the next tranche of the Fund's loan to Greece until "all uncertainty is removed."
Greek officials had previously warned that the country -- which is labouring under a debt mountain of 350 billion euros -- only had enough money to pay its bills until mid-November.
Papandreou claimed in Cannes that Greece had "quite a few days" ahead to pay wages and pensions without resorting to loan funds.
But Venizelos appeared to contradict him, saying that the loan funds "have to be disbursed without delay."
Copyright AFP (Agence France-Presse), 2011