| Silvio's supporters in the senate will move a confidence motion while opponents will seek a no-confidence vote [AFP]
The Italian prime minister is only a few hours away from knowing whether a close parliamentary confidence vote will force him out of office or cement his image as one of the great survivors of Italian politics.
Silvio Berlusconi said he was confident of victory as he arrived in the senate for the vote on Tuesday morning.
The 74-year-old is expected to win a morning confidence vote, but the outcome of a second no-confidence measure in the lower house, brought by his former ally Gianfranco Fini, will lie in the hands of a few politicians.
Berlusconi has previously defied critics, winning three elections since 1994 despite a string of gaffes and scandals.
But he has been weakened by the breakup with Fini, which cost him a parliamentary majority, and further by allegations he partied with prostitutes and passed laws to protect his position.
Single vote may decide
Tuesday's vote in both the chamber of deputies and the senate could be decided by as little as a single vote, political commentators said.
The no-confidence vote has been brought by the opposition and rebel centre-right deputies loyal to Fini.
The government has also put forward a confidence motion in the senate where it has a majority.
Analysts have estimated that Berlusconi may just have the numbers to survive with 314 possible votes against 313 for the combined opposition.
In an address to parliament on Monday, the prime minister said: "If the government has to operate well, it must be left to people to decide and this is part of our constitution and sovereignty.
"If this principle is violated, then it means that the spirit has been betrayed. And those in parliament have to interprete the wish of the people."
The vote comes as Berlusconi - accused of paying for sex and paying the Mafia to protect his family and busines interests - wades through one of his toughest years in 2010.
A split with a group led by Fini in July cost him a secure parliamentary majority and after months of stalemate, a no-confidence motion in parliament seems likely to be decided by just one or two votes.
Guido Moltedo, a political commentator in Rome, told Al Jazeera that the vote was a "turning point" for Italy "even if Berlusconi succeeds in having a majority [of the vote]".
"Everything is going to change ... in this country; and the confusion will be great according to me in both cases: if Berlusconi wins a majority or if he loses the confidence vote," he said.
"Berlusconi can go away in the near future but the situation is the country will not be much better ... because the opposition is fragmented and fractious."
The prime minister has been predicting he will win, but if he loses he will have to resign, halfway through the five-year term of parliament.
The result may depend on last-minute changes of heart or outside factors such as whether any of three pregnant deputies expected to vote against the government have to be absent from the chamber.
The vote will be closely watched on bond markets which are on high alert over the euro zone debt crisis and which could turn on Italy, one of the most heavily indebted countries in Europe, if the situation threatens financial stability.
Even if Berlusconi scrapes through, there is little confidence that he will have the strength to push through the kind of reforms authorities such as the Bank of Italy believe are needed to address deep-seated problems in the economy.