Euro zone finance ministers had cancelled face-to-face talks on the US$170 billion deal today, saying they had yet to receive written pledges from Greek political party leaders to stick to punishing spending cuts, or clarification of all the savings.

"The letter will be dispatched within the day," a New Democracy party source told Reuters on condition of anonymity. Doubt has focused on Samaras, Greece's likely next prime minister and a strong critic of the austerity measures.

Ministers of the Eurogroup downgraded the Brussels meeting - originally planned for 1700 GMT - to a conference call.

Greece needs the funds by next month to avoid a messy bankruptcy.

The Eurogroup is next due to meet on Monday, but Greece has said it must initiate a debt swap deal with private sector bondholders by Friday if it is to meet a March 20 for 14.5 billion euros in debt repayments.

The Eurogroup had asked Greece to clarify how it would fill a 325-million-euro gap in budget cuts promised for 2012 and to persuade all party leaders to sign a commitment to implement austerity measures after an election expected in April.

"It's true we are asking the Greeks for some extremely painful sacrifices and I understand their anger, but Greece has made many errors in its past," French Foreign Minister Alain Juppe told France Info radio on Wednesday.

"It (the bailout) must be concluded because if Greece went bankrupt and left the euro zone, the chaos would be even worse for the Greek people and very bad news for the euro zone."

The cabinet of Prime Minister Lucas Papademos discussed the gap in the 3.3-billion-euro austerity program late into Tuesday evening. But there was no official clarification of where the savings would come from.