Premier Silvio Berlusconi (search), fighting to survive the worst political crisis of his four-year tenure, will put his government to a vote of confidence this week, officials said Tuesday.

He has been clinging to power since his center-right coalition suffered a crushing defeat in this month's regional elections. Even his allies have called for his resignation.

The vote is scheduled for Thursday, parliament officials said. If Berlusconi loses, the government must resign. On Wednesday, the premier is scheduled to speak first in the Senate and then in parliament's lower house, presumably to make his case.

It was unclear who demanded the vote of confidence, but it had been widely expected after Berlusconi resisted calls from his own allies to step down and reshuffle the Cabinet.

In a statement issued Tuesday, Deputy Premier Gianfranco Fini (search) — the premier's most important ally in the governing coalition — expressed "regret" that Berlusconi had not resigned.

Fini said continued participation by his National Alliance party in the governing coalition "depends solely on what Berlusconi will say and do." He said the party's leaders would meet after Berlusconi's addresses to parliament Wednesday.

The opposition contends the government is no longer able to run the country and is pressing for early elections, currently scheduled for spring 2006.

"There's no government anymore. The only one who doesn't seem to realize is Silvio Berlusconi," said opposition lawmaker Willer Bordon, according to the ANSA news agency.

Berlusconi's coalition has enjoyed a solid majority in parliament and may still have the numbers to survive the confidence vote.

The Union of Christian Democrats (search) withdrew its ministers from the government last week but has said it will continue to support Berlusconi in parliament. The party said its goal was to push Berlusconi to form a stronger government — not cause the coalition's downfall.

Berlusconi's decision Monday not to step down surprised even his allies.

After his defeat in the regional vote, Berlusconi proposed a Cabinet shuffle and a revised program to relaunch the coalition ahead of the general election next year. The proposal was rejected by the Christian Democrats.

They wanted him to form a new government with a new platform — a technique past Italian premiers have used to strengthen faltering coalitions. Berlusconi refused out of concern for his credibility.

Berlusconi, whose coalition won power in 2001, has expressed hope that his government would be the first in postwar Italy to serve out a full five-year term. But analysts said he was losing his grip.

The coalition "seems on the verge of dissolving," political analyst Stefano Folli wrote in Tuesday's edition of the newspaper Il Sole 24 Ore. "After yesterday, it is difficult to imagine that Berlusconi can patch things up in a few hours or a few days."

Berlusconi's troubles have been touched off by a weak economy and his support for the Iraq war in spite of widespread opposition here to the U.S.-led invasion.

One of Berlusconi's most contested decisions was to send troops to Iraq after the ouster of Saddam Hussein. Pressure to pull them out mounted after the March 4 death in Baghdad of an Italian intelligence agent who was escorting a recently released hostage to freedom. He was killed by U.S. troops who opened fire on his vehicle.