"I was never convinced that war was the best system to bring democracy to the country and to get rid of a bloody dictatorship," Berlusconi said. "I tried several times to convince the American president to not go to war."
His comments came in an interview with the La7 private television station that is to be broadcast on Monday - the same day Berlusconi is due to meet Bush in Washington.
Berlusconi is facing a tough re-election battle next year, and his popularity has fallen in part because of Italians' continued opposition to the war.
Excerpts of the interview were reported on Saturday by the Apcom and ANSA news agencies.
"I tried to find other ways, and other solutions, even through an effort together with [Libyan leader Muammar al-Qadhafi]. We didn't succeed, and there was the military operation.
"I believed that military action should have been avoided," he was quoted as saying.
Italian agent killed
Berlusconi was one of Bush's strongest supporters in the run-up to the Iraq war. On the eve of the conflict in March 2003, he told Italian lawmakers that using force against Iraq was legitimate and that Italy could not abandon America "in their fight against terrorism".
Italy did not send any combat troops to Iraq, but it sent 3000 troops after the fall of Saddam Hussein to help maintain security and rebuild the country.
Italy sent a 3000-strong military
contingent to Iraq in 2003
While still supporting Bush, the Italian government has clashed with Washington over the Iraq conflict, in particular over the killing of an Italian agent by US forces last March.
Berlusconi has also had to deal with declining popularity because of sluggish economic growth and continued opposition to Italy's presence in Iraq.
Opposition leader Romano Prodi, who opposed the war, has said he will replace Italian troops in Iraq with a civilian force if his centre-left coalition wins.
Italy's defence minister said in comments published on Saturday that it was "plausible" that the remainder of Italy's 2900-strong contingent would return home in the first half of 2006.
Recently, an initial contingent of 300 soldiers returned home and Berlusconi has said subsequent groups of 300 would come back until the final group of 1000 returns together.