Italy’s parliament is due to hold a vote of confidence in the governing coalition, with an attempt to topple PM Enrico Letta appearing to falter.
The vote was called after Silvio Berlusconi ordered ministers in his centre-right People of Freedom party (PDL) to leave the government.
But on the eve of the vote, leading PDL figures defied him, saying they would back Mr Letta.
Mr Letta has rejected the resignations of the five PDL ministers.
Berlusconi, a former prime minister, has accused Mr Letta of allowing his “political assassination through judicial means” – a reference to his criminal conviction for tax fraud in August.
“Even though I understand the risks that I am taking on, I have decided to put an end to the Letta government,” Berlusconi said in a letter to the weekly magazine Tempi.
But in an apparent break with Berlusconi, his deputy and party secretary Angelino Alfano said PDL MPs should back Mr Letta in Wednesday’s confidence vote.
“I am firmly convinced that our party as a whole should vote confidence in Letta,” said Mr Alfano, who is also Italy’s interior minister.
His comments caused the Italian stock market to jump on Tuesday as investors appeared increasingly confident that the government would not fall.
Silvio Berlusconi in parliament. 30 Sept 2013
Silvio Berlusconi ordered his five PDL ministers to quit on Saturday
Another once-loyal supporter, Carlo Giovanardi, a senator from Berlusconi’s party, said 40 PDL senators were ready to vote for the government.
“We want to remain a moderate force,” he said.
Fabrizio Cicchitto, a PDL deputy, said: “Making the government fall would be a mistake.”
Mr Cicchitto said any new government would be “hostile to the PDL” and would be a boon for Mr Letta’s centre-left Democratic Party.
On Tuesday, Mr Letta refused to accept the resignations of five ministers from the PDL, Italy’s Ansa news agency reported, citing a government source.
Mr Letta called the vote of confidence after Berlusconi ordered his ministers to leave the government in protest at a rise in VAT (sales tax).
The prime minister accused Berlusconi of using the issue as an “alibi” for his own personal concerns.
Analysts say the crisis threatens to hamper badly needed reforms to tackle Italy’s economic problems that include debt, recession and high youth unemployment.
The International Monetary Fund has warned that political tensions are a risk to the Italian economy.
Mr Letta’s cross-party alliance was formed in April after two months of political deadlock following an inconclusive election.
Berlusconi dominated Italian politics for nearly two decades before resigning in November 2011, in the midst of a storm over the failing economy.