ROME — Former Premier Silvio Berlusconi, who announced this week he wouldn't run in spring elections, says he now feels compelled to stay in politics to reform Italy's justice system after being convicted of tax fraud.

Berlusconi's comments came hours after a Milan court sentenced him to four years in prison and barred him from public office for five years. The sentence isn't definitive until all appeals are exhausted, and Berlusconi's lawyers vowed to appeal.

Berlusconi denounced the judges as politicized, as he has done in his many legal wranglings with Italian magistrates. He told his private Mediaset television Saturday that he felt "obliged to stay in the game to reform the justice system so that what happened to me doesn't happen to others."

He didn't say in what capacity he would work.