Rome - Italy's Silvio Berlusconi on Wednesday abandoned his bid to topple Prime Minister Enrico Letta, saying he would vote to support the government in a humiliating climbdown after key allies rebelled.
"We have decided to vote for confidence, not without internal disputes," Berlusconi said ahead of a confidence vote in parliament called after he launched his challenge to the leadership on Saturday.
Berlusconi said he had changed his mind on Wednesday after hearing Letta's promise to lower taxes and "the need for a government that can carry out institutional reforms in Italy".
The surprise about-turn made victory for Letta's coalition a certainty and was immediately cheered by the markets, with shares in Milan jumping 1.45% higher after the shock announcement.
Letta shook his head as Berlusconi was speaking and the address was followed by stunned silence.
Lawmakers were still set to vote despite the change of heart by a man who has dominated Italian political life for much of the past two decades.
Letta earlier asked lawmakers to vote for him, saying Italians were tired of "blood in the arena".
"Italy runs a risk that could be a fatal risk. Seizing this moment or not depends on us, on a yes or a no," Letta said in his address to the Senate.
"This is an historic situation," he said.
Several key figures from Berlusconi's own centre-right People of Freedom party (PDL) broke ranks with the billionaire media mogul after his decision to call time on the government and pull his ministers from the cabinet on Saturday.
Letta immediately condemned the move as "crazy and irresponsible" and Interior Minister Angelino Alfano, national secretary of Berlusconi's party, reacted by saying he would be "pro-Berlusconi in a different way".
A letter doing the rounds in the Senate just before Berlusconi spoke had 23 signatures of PDL senators willing to defy their leader.
Together with votes from four rebels of the anti-establishment Five Star Movement, this would have been sufficient for Letta to win a majority even without Berlusconi's support.
"Italians are crying out that they cannot take any more blood in the arena, with politicians who slit each other's throats and then nothing changes," said Letta, a 47-year-old moderate leftist.