Instead, ministers opted to delay a decision until July 3. By then, according to Mr. Venizelos, the Greek Parliament should have approved the tough austerity program upon which more aid is conditioned.

But the second problem underlines how complex the rescue of Greece has become. To release the I.M.F. share of the €12 billion, Mr. Lipsky insisted on an assurance that the European Union would underwrite the finances of the Greek state for the next year — a much tougher position than European officials expected.

“We will all require assurances that the program is financed and that involves assurances from our Eurogroup partners that adequate finance is available,” Mr. Lipsky told reporters. “That needs to be done before we can move forward and we are hopeful that those conditions will be met with alacrity.”

With a debt-laden Greek economy unable to return to the financial markets this year or next, its finances will inevitably be dependent on a second bailout package that European ministers have yet to draw up. Its construction has been delayed by a dispute over the role of banks and other private lenders in any future bailout. That argument was largely resolved by the leaders of France and Germany in Berlin last Friday, but the outcome means that the European Union must now seek voluntary contributions from bondholders.

E.U. diplomats expect Jean-Claude Trichet, president of the European Central Bank, to play a leading role in rounding up pledges to roll over maturing loans back into Greece’s coffers. But the amount that would be counted as part of the bailout remains far from clear, leaving European governments in the dark about their own contribution.

The delay until July 3 gives them a little more time to work out how much they need to pledge to satisfy an I.M.F that appears increasingly assertive under Mr. Lipsky. In a statement released Monday on euro zone policies, the I.M.F. said it was “essential to bring the unproductive debate about debt reprofiling or restructuring to a close quickly.” It also gave a stark warning about the risk of contagion to other countries, starting with Ireland and Portugal but possibly spreading to Spain, Italy and even Belgium as well. “With deeply intertwined fiscal and financial problems, failure to undertake decisive action could rapidly spread the tensions to the core of the euro areas and result in large global spillovers,” the fund said.