A default is not an option Greece can allow to happen, Greek interim Prime Minister Lucas Papademos said on Friday evening.

"A Greek default is not an option we can allow to happen. We must do whatever necessary to push through the new debt deal," Papademos said when addressing a televised cabinet meeting amidst an unfolding government crisis.

A total of six ministers and deputy ministers quit from the three-party administration over a new set of austerity measures pushed by the government in return of a fresh international aid package to avert a Greek bankruptcy next month.

They include Alternate Foreign Affairs Minister Mariliza Xenogiannakopoulou and Deputy Labor Minister Yiannis Koutsoukos from the socialist PASOK party.

They were joined by all four ministers who belong to the rightist Popular Orthodox Rally (LAOS), including Transport Minister Makis Voridis, Deputy Shipping Minister Adonis Georgiadis, Deputy Defense Minister George Georgiou and Deputy Agriculture Minister Asterios Rondoulis.

"Those who do not agree and will vote against the bailout program can not remain members of this cabinet," said Papademos, adding that it is an hour of historic responsibility for everyone, since what is at stake is the future of the country.

Papademos will proceed to a wide cabinet reshuffle in the coming days, most probably early next week, following a crucial parliamentary vote over the austerity package scheduled for Sunday evening, local media cited government sources as saying.

Political analysts in Athens expressed anxiety over whether the parliament will pass the measures or collapse.

LAOS party leader George Karatzaferis said on Friday the 16 deputies of his party will reject the package, while over a dozen PASOK lawmakers and a smaller group of MPs from New Democracy, the conservative party in the coalition administration, warned that they will cast negative votes.

Three months ago, Papademos' administration won a confidence vote with more than 250 votes in the 300-member-strong assembly, with the support of the three parties.

But if Greece fails to ratify the deal clinched on Thursday, international creditors warned that they will not release to the debt-laden country further multi-billion-euro funding in the coming weeks.

In such a case, Greece faces a chaotic bankruptcy in March that would send shockwaves across the eurozone and global economy and a Greek exit from the euro.