ROME — A prosecutor has asked Italy's highest court to uphold Silvio Berlusconi's tax fraud conviction and four-year jail sentence, but to reduce his ban on public office to three years from five.

Prosecutor Antonello Mura made that recommendation during a hearing on Tuesday. He said the shorter ban would reflect changes in sentencing law.

Berlusconi's defense lawyer, Franco Coppi, said the prosecutor is trying to rectify "a blatant error" in a lower court's sentencing, which has been confirmed on appeal.

Italy's highest court is hearing arguments in the former premier's appeal of his tax fraud conviction.

The tensely awaited decision, which could impact Italy's fragile government, isn't expected before Wednesday.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

Silvio Berlusconi's political fate is in the hands of Italy's highest court, which was hearing arguments Tuesday in the former premier's challenge to a fraud conviction.

The tensely awaited decision, which could have an impact on Italy's fragile, three-month-old coalition government, is expected Wednesday or possibly Thursday, Berlusconi's lawyer Franco Coppi told reporters outside the courtroom. Berlusconi's case is one of eight on the docket, and the last one to be heard.

"I'm superstitious and I don't make predictions," Coppi said during a break after the court spent two and a half hours summarizing the case, but he added: "I expect to win."

Berlusconi, 76, was convicted with three others in Milan last October of tax fraud in a complex TV rights transaction for his Mediaset network, and sentenced to four years in prison with a five-year ban on public office. A Milan appeals court upheld the lower court's decision this spring. This is his final appeal.

Defendants rarely attend hearings at the court, and Berlusconi was not present. A dozen police officers were posted in the court room, many more than are usually present even during other high-profile cases, to enforce a ban on taking photos and using telephones.

The three-time former premier has no official role in Italy's uneasy coalition government, but remains influential and was key to the center-right's close, second-place finish in February elections. He won a seat in Italy's Senate, which he would have to vacate if the lower courts' verdicts are confirmed.

Berlusconi has appealed to center-right lawmakers not to yank their support from the cross-party government of Enrico Letta if his conviction is confirmed. Letta's government is already having trouble mustering support for a series of measures to help Italy out of recession, although the premier said Monday that he is not worried about the decision's impact on his government, and that "Italy is more stable than you expect."

Despite politicians' attempts to spread calm, political analysts said the situation remains volatile.

"The problems is that in the case of a conviction, the dynamic could overwhelm the wishes of individuals," Stefano Folli, a political analyst for il Sole 24 Ore business daily, wrote Tuesday. "A convicted Berlusconi would become a martyr for his backers while at the same time being an unacceptable ally for a good part of the center-left."

The high court is limited in its scope to examining whether errors were made at the trial or earlier appeal. It does not hear new witnesses or receive new evidence.

If the court upholds the conviction, Berlusconi will be immediately stripped of his Senate seat and barred from running for any election. It is unlikely he would serve jail time, as three years would be shaved off in a general amnesty aimed at emptying prisons and it is unusual to serve time for short sentences, especially given Berlusconi's age.

The court could throw out Berlusconi's conviction, but such rulings are rare. Another possibility is that it could order a new appeals trial before a different judge. If that happened, the statute of limitations would likely kick in for at least some of the alleged offenses, resulting in a milder sentence if Berlusconi is convicted again, and maybe sparing him the ban on holding public office.

Indicative of the high stakes in this case, Berlusconi for the first time in two decades of court cases has reached beyond his longtime defense team to tap Coppi, a highly reputed appellate lawyer, to argue before the court.

In a separate criminal case yet to come to appeal, Berlusconi faces a possible lifetime ban on holding public office if a lower-court conviction for paying for sex with a minor and using his office to cover it up is upheld. That verdict in June also dealt him a seven-year prison sentence.

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Colleen Barry contributed from Milan.