ATHENS, Greece — Greek Prime Minister George Papandreou called for the activation of a joint eurozone-International Monetary Fund financial rescue to pull his country out of a major debt crisis.

Papandreou, saying market pressure threatened to derail the country's economy, announced today he had asked Finance Minister George Papaconstantinou to make a formal request for the plan's activation.

The plan aims to cover Greece's immediate borrowing needs so it can continue servicing its debt and avoid default. The bailout would have to be reviewed by the European Union executive and the European Central Bank, and needs approval by all 15 of the other governments that use the euro.

"It is a national and pressing necessity for us to formally ask our partners for the activation of the support mechanism, which we jointly created in the European Union," Papendreou said.

Papandreou said the markets had not responded positively to Greece's austerity measures that were designed to pull the country's disastrous finances into line.

"Today, the situation in the markets threatens to deconstruct, not only the sacrifices of the Greek people, but also the smooth course of the economy," he said.

The rescue package will provide Greece with loans from other eurozone countries to the tune of 30 billion euros at interest rates of about 5 percent, and about 10 billion euros from the IMF.