The Greek prime minister has stunned the world by saying he will put his country's debt-relief deal with the European Union to a public vote and abide by the voters' decision.

Prime Minister George Papandreou's announcement sent global stock markets plummeting as investors reacted to a major jolt of uncertainty in the European economy.

Mr. Papandrou told a Cabinet meeting Tuesday that the Greek people will be asked whether they want to keep using the euro currency. He said any deal will only be implemented with the consent of the Greek people, and that he hopes any turmoil caused by his unexpected announcement will be only temporary.

A number of lawmakers in the prime minister's Socialist Party oppose an up-or-down public vote, which would come early next year. Some party members are demanding Mr. Papandreou's resignation, and his government faces a no-confidence vote Friday in Parliament.

Mr. Papandreou has strongly supported the European Union plan to cut Greece's debt, which would obligate severe domestic spending cuts and tax hikes. It also would eliminate jobs now held by thousands of public employees.

Terms of the latest deal offered by the EU call for European banks to forgive 50 percent of Greece's debt. That appeared to calm nervous markets at first, but then Mr. Papandreou told Socialist lawmakers Tuesday that he will honor results of the referendum.

EU leaders Herman Van Rompuy and Jose Manuel Barroso said they “fully trust” Greece to uphold last week's eurozone debt-relief agreement. French President Nicolas Sarkozy said letting people vote is “always legitimate,” but that a Europe-wide agreement is the only possible way to resolve the debt crisis.

World Bank president Robert Zoellick said that if voters reject the plan, “It's going to be a mess.”

Mr. Sarkozy and German Chancellor Angela Merkel plan to meet Wednesday in Cannes, France, with leaders from the International Monetary Fund and Greece to discuss the latest snag in solving the continent's debt crisis.