Mr. Venizelos, who was to meet on Sunday with Christine Lagarde, the managing director of the I.M.F., also said that he expected the next allotment of funds to be released soon.

“Greece is and will always be a member of the euro, a member of the euro zone,” Mr. Venizelos said.

That Mr. Venizelos had to come out and insist that Greece was not leaving the euro zone — until recently an unspoken article of faith in Greece — underscored how close the country has come to defaulting on its debt and how dangerous such an outcome could be, not just for the euro zone but for a global economy teetering on the verge of recession.

With Greek government debt trading on the open market below 40 cents on the dollar, it is quickly approaching what debt experts call the recovery rate — the price investors would get for their bonds if the country officially defaulted.

In effect, that means investors have given up.

The Greek government has moved to reassure investors, rolling out new austerity measures that include plans to lay off 50,000 public sector workers and to make deeper cuts in wages and pensions. But the Greek economy is expected to shrink 6 percent this year and 2 percent next, and unemployment, already at 16 percent, is ticking up toward Spain’s level of 20 percent.

Even with fresh aid coming in, investors see little chance that Greece, facing such harsh economic conditions, will be able to cope with a debt burden that the I.M.F. now expects to hit 190 percent of gross domestic product next year.