"It goes without saying that whoever disagrees and does not vote for the new program cannot stay in the government," he said in a televised speech to his cabinet following the resignation of several ministers and their deputies.

A tumultuous day inside the Parliament was matched on the streets outside, where protesters throwing fire bombs clashed with the police and Greek workers walked off the job in the second general strike this week in protest against new austerity measures the country must take to avert a disastrous default next month.

Adding to the anxiety surrounding negotiations over an international bailout for Greece, the leader of the smallest of three parties in the governing coalition said he would vote against an austerity package Greek lawmakers agreed to Thursday after marathon negotiations. "The creditors are asking for 40 years of submission," the politician, Georgios Karatzaferis, who heads the right wing party, Popular Orthodox Rally, told reporters. "Greece will not give itself up."

Mr. Karatzaferis party controls only 16 seats in Parliament, however, not enough to scuttle the deal if most of the other members of the coalition, the Socialists and New Democracy, support it. It would take a huge backbench rebellion for the vote to fail as the two largest parties still have 236 mps in the 300-member house.

In his speech, Mr. Papademos said his highest priority was guaranteeing Greece's solvency. He said that the new economic program was the product of tough negotiations with creditors and would eventually bring the country back to growth.

The prime minister said it was time for the cabinet to show "historic responsibility" in a difficult time. "The endurance of the government is being tested and it is clear that not everyone can endure this burden," he said in an apparent reference to the two ministers and four deputy ministers who have resigned over the past two days.

According to local news media outlets, Mr. Papademos plans to announce a new cabinet on Monday, which put in doubt late on Friday a parliamentary vote on the new measures scheduled for Sunday.

Mr. Papademos went to some lengths to explain in his speech the terrible repercussions of a disorderly default. "It would create conditions of uncontrolled economic chaos and a social explosion," he said. "The state would be unable to pay wages and pensions and cover basic operational costs such as those of hospitals and schools."

Imports of basic goods like fuel and medicine might become prohibitively expensive, he said, and businesses would close down en masse. "The living standard of Greeks would collapse and the country would be dragged into a spiral of recession, instability, umemployment and misery," he said. "All these developments would lead, sooner or later, to Greece's exit from the eurozone."

The general strike came a day after the government reached a provisional deal with the so-called troika of foreign lenders — the European Commission, the European Central Bank and the International Monetary Fund — on the terms of a new loan program. The government of Prime Minister Lucas Papademos pledged to cut private-sector wages by more than 20 percent, lay off thousands of civil servants and slash public spending.

But skeptical creditors have demanded additional cuts to cover a $430 million shortfall created by the refusal of political leaders to slash supplemental pensions as well parliamentary approval and written commitments to the terms of the deal from the leaders of the three parties in Mr. Papademos's coalition before additional financing is released.

"Unfortunately, the euro group did not take a final, positive decision," Finance Minister Evangelos Venizelos said in the early hours of Friday after a grueling summit with euro zone peers talks in Brussels. "Many countries expressed objections, based on the fact that we did not fully complete the list of additional measures required to meet our targets for 2012." But he urged Greeks to support the additional measures demanded by the lenders.