FILE - In this file photo taken Dec. 29, 2012 Silvio Berlusconi smiles as he arrives at Milan's central train station, Italy. Italy's top court confirmed Thursday, Aug. 1, 2013 Berlusconi tax fraud conviction, and ordered the review of a political ban contained in the sentence that was appealed by the Italian media Mogul. AP Photo/Luca Bruno, file Italy's highest court President Antonio Esposito, third right, read the sentence confirming a four year term for Italian media Mogul and former Premier Silvio Berlusconi for tax fraud in Rome, Thursday, Aug. 1, 2013. Italy's highest court upheld Berlusconi's four-year prison sentence for tax fraud, the first time the former premier and billionaire media mogul has definitely been convicted of any crime. The tensely awaited ruling, however, ordered a review a five-year ban on public office that was part of the lower court's sentence. AP Photo/Alessandro Di Meo, pool Italy's highest court President Antonio Esposito arrives to read the sentence confirming a four year term for Italian media Mogul and former Premier Silvio Berlusconi for tax fraud in Rome, Thursday, Aug. 1, 2013. Tv camera tripods stand outside the Court of Cassation building where Berlusconi's case on tax fraud will be decided, in Rome, Thursday, July 31, 2013. Berlusconi's political fate is in the hands of Italy's highest court, which is preparing to hear arguments in the former premier's fraud conviction. Berlusconi has been convicted 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. This is his final appeal. AP Photo/Gregorio Borgia A demonstrator holds a sign reading in Italian "Guilty for the justice, acquitted by the political system" outside Italy's highest court building where Berlusconi's case on tax fraud will be decided in Rome, Thursday, Aug. 1, 2013. Silvio Berlusconi's fate hung in the balance Thursday as Italy's highest court deliberated on his last-resort appeal of a tax fraud conviction that could halt, at least temporarily, his political career. AP Photo/Riccardo De Luca ROME (AP) - Italy's three-time former Premier Silvio Berlusconi for the first time in two decades of criminal prosecutions related to his media empire was definitively convicted of tax fraud and sentenced to four years in prison Thursday by the nation's highest court. The tensely awaited decision was described as a historical moment by opposition politicians and puts fresh pressure on Premier Enrico Letta's fragile coalition government. He needs the support of both Berlusconi supporters and his own center-left Democratic Party to push through reforms to get Italy out of recession, and the ruling is likely to have a destabilizing impact. Judge Antonio Esposito, in reading the court's decision, declared Berlusconi's conviction and prison term were "irrevocable," though he ordered another court to review the length of a ban on public office. Lower courts had put it at five years, but a state prosecutor recommended in its arguments this week that it be lowed to three, citing conflicts in the relevant sentencing laws. How the government is affected by the ruling is likely to emerge in comings days. On the one side, Berlusconi supporters may withdraw support in protest, while center-left lawmakers may find it unpalatable to continue in a coalition with a party whose leader has been convicted of defrauding the state of tax income. Beppe Grillo, the leader of the anti-establishment 5 Star Movement, declared on his blog: "Berlusconi is dead." He compared the conviction to the fall of the Berlin Wall in 1989 that helped bring down Soviet communism. Berlusconi's exit from the political scene he has dominated for two decades is unlikely to be quiet. A Milan appeals court will now have to determine the length of a public office ban. And then, the Senate, where Berlusconi holds a seat, will have to debate and vote on revoking his seat as part of a process that can stretch for months, if not a year. If the Senate opposes it and refuses to formally revoke Berlusconi's seat, the high court could turn to the constitutional court in a bid to resolve the standoff. Berlusconi is highly unlikely to actually go to prison. Three years will be shaved off as part of a general pardon for crimes committed before 2006 aimed at easing prison crowding, and it is unusual for defendants to serve sentences of just one year for a first offense, particularly at Berlusconi's age, 76. He would likely be given the choice to serve the remaining year under house confinement or opt for social services. Berlusconi awaited the sentence at his residence in central Rome with his lawyers, deputy party leader Angelino Alfano and his eldest daughter, Marina, all of whom were seen entering the building in the hours leading up to the announcement. He issued no immediate reaction. Barry contributed from Milan.