Greece will hold a controversial referendum on a European bailout plan in early December that European leaders said Wednesday will determine whether or not it stays in the eurozone.

Greece won't get any new international loans until then, European leaders said after heaping pressure on Greece's prime minister at emergency talks Wednesday.

"The referendum ... in essence is about nothing else but the question, does Greece want to stay in the eurozone, yes or no?" said German Chancellor Angela Merkel at a press conference.

The statement, echoed by French President Nicolas Sarkozy at her side, was the clearest acknowledgement to date that pulling out of the eurozone is a possible outcome.

Luxembourg Prime Minister Jean-Claude Juncker announced that the referendum would be held Dec. 4, after a meeting with Greek Prime Minister George Papandreou and other European leaders in the French city of Cannes. Sarkozy said the vote would be Dec. 4 or 5.

Sarkozy said the next installment of Greek rescue loans, which had already been approved and were due to be paid in November, cannot be paid until after the referendum.

"We want to continue with the Greeks but there are rules and it's unacceptable that these rules are not followed," Sarkozy said.

The chief of the International Monetary Fund, Christine Lagarde, said "I hope that this whole thing can be closed and completed by mid-December — I think it's important from a cash point of view."

Papandreou's stunning announcement Monday that he would stage a  referendum roiled world financial markets and threw into question an ambitious and costly European deal worked out in torturous negotiations a week ago.

Merkel confirmed that Greece did not inform the rest of the eurozone about the referendum. "This did not happen in a co-ordinated fashion," she said.

She and Sarkozy summoned Papandreou to Cannes for talks Wednesday at which European leaders expressed their anger and pressed him to hold the referendum as soon as possible.

 A "no" vote in the referendum would have enormous consequences not just for Greece but for the rest of Europe. It could lead to a disorderly Greek default, force Greece out of the 17-nation eurozone, topple many fragile European banks and send the global economy spinning back into recession.

Papandreou's gamble to put the hard-won €130 billion ($181 billion) deal to his austerity-fatigued electorate caused market turmoil Tuesday as investors fretted over the prospect of a  disorderly Greek debt default and the country's exit from the euro.

His announcement also sparked a rebellion among his governing Socialist lawmakers. A crucial test of party loyalty will come during a vote of confidence on Friday in parliament, where the Socialists have a two-seat majority.