Greek Prime Minister George Papandreou faces a confidence vote in his government today that may determine whether Greece becomes the first euro-area country to default.

Tonight's vote caps a week of turmoil for Papandreou, who fended off a revolt from the ranks of his ruling socialist Pasok party in parliament last week. That came after opposition parties rejected his call for a national unity government. European Union leaders have insisted Papandreou secure multi-party support for austerity measures that are a condition of the aid needed to avoid default as soon as next month. A vote on the fiscal plan is due next week.

“Pasok now knows it has to close ranks,” said Holger Schmieding, chief economist at Joh. Berenberg Gossler & Co. in London. “The situation is volatile. A negative vote by the Greek parliament could trigger a serious crisis in Europe.”