ATHENS — Finance Minister Evangelos Venizelos of Greece left for a meeting of his counterparts in Brussels on Thursday morning after Greek political leaders failed to reach an agreement on austerity measures demanded by Greece’s financial backers in return for a €130 billion bailout.

After more than seven hours, talks stalled early Thursday between Prime Minister Lucas D. Papademos and the three political leaders in his government, who agreed on a range of drastic wage cuts and public sector layoffs but failed to find consensus on more than €300 million in pension cuts demanded by Greece’s foreign lenders.

According to the local news media, Greece’s foreign creditors have given the authorities 15 days to find a way to raise €300 million without cutting pensions. The creditors are said to have projected €635 million in savings from reductions to pensions. The Greek authorities reportedly plan to cut €325 million from defense spending but still have to plug a €300 million shortfall.

The three party leaders in the Greek coalition are said to have authorized Mr. Papademos to negotiate this shortage with creditors.

If agreement is not reached on this relatively small sum, the lenders will not give Greece the $170 billion in aid it needs to prevent a default as soon as a bond comes due March 20. Failure to reach an accord could jeopardize a bond swap under which private investors would take losses of as much as 70 percent, a deal that must be completed well before the bond comes due.

But even as Mr. Venizelos appealed to the political leaders for the umpteenth time, saying that their decisions “will determine whether the country remains in the euro zone or whether its place in Europe will be endangered,” the line between Greek political theater and international financial trauma was difficult to discern. And after weeks of delays and threats from both sides — many of them empty — it was clear that the credibility of both Greece and its lenders was on the line.

In a sign that an agreement was still expected, Mr. Papademos’s office said in a statement early Thursday that the three parties had agreed on all issues except one and that they would continue the discussion “immediately.” But as Mr. Venizelos left for Brussels, it was not clear that the pension issue would be resolved before the meeting, scheduled for 5 p.m. local time. A Greek parliamentary vote on the full package of measures is scheduled for Sunday.

The country’s two main labor unions called for a strike for Friday and Saturday to protest the new proposed package of austerity measures. Union leaders said protest rallies would be held outside Parliament on both days of the strike and on Sunday during the vote.

After breaking talks with Mr. Papademos and issuing statements, the three political leaders retired to their homes for the night about 2 a.m.

A little while earlier, while Mr. Papademos was holding talks with Greece’s foreign lenders, one of the three leaders participating in the government, George Karatzaferis, the leader of the Popular Orthodox Rally, issued a statement after 1 a.m., saying that he was unwilling to agree to the terms of the new bailout and indicating that he might withdraw from the government.

That would leave the burden of accepting the austerity measures on the other two parties in the coalition, the Socialists and the center-right New Democracy party.

Although Greece’s so-called troika of foreign lenders — the European Commission, the European Central Bank and the International Monetary Fund — have indicated that they will ask for written agreements from the party leaders that they will support the loan agreement, the government is still expected to be able to approve the agreement without Mr. Karatzaferis’s party.

Even if he does pull out of the coalition, the government will have a majority in Parliament, where the Popular Orthodox Rally has only 16 of the coalition’s 252 seats. With elections expected as soon as April, the parties are fighting for political survival.