Greek cabinet ministers, in an all night emergency meeting, say they will support the Prime Minister's call for a referendum on an EU debt bailout deal.
George Papandreou's surprise announcement on Monday pummelled the euro and global stocks.
Some of his party lawmakers called for him to quit for jeopardizing Greek euro membership.
But the cabinet support gives him stay until a confidence vote in parliament on Friday.
The referendum is expected to take place as soon as possible.
Later, Papandreou will face leaders of France and Germany for crisis talks in Cannes, before the G20 summit.
Whatever the result of the vote, Papandreou's gamble guarantees long weeks of uncertainty.
This comes at a time when the 17-nation currency area was desperate for a period of calm to implement
remedies agreed last week to overcome its sovereign debt crisis.
Marie-Claire Fennessy, Reuters