The moderate left-wing opposition called for the immediate return of the soldiers, a day after Berlusconi himself expressed revulsion at the abuse of Iraqi prisoners in British and US detention documented in a leaked report by the International Committee of the Red Cross.

"Berlusconi must come before parliament before he goes to the United States next Thursday and say that he is no longer acting as a vassal," said Francesco Rutelli, leader of the centre-left Olive Tree coalition.

"If that is not done, we will vote for the return of our soldiers," he told Italy's Repubblica newspaper.

Berlusconi is heading to Washington on May 19, shortly before US President George W. Bush visits Italy in June to celebrate the 60th anniversary of the liberation of the city from the Nazis during World War II.

Italy has 3,000 troops serving with the occupation forces in Iraq, third in size only to the United States and Britain, whose governments are scrambling to contain the firestorm over the prisoner abuse.

Olive Tree parties have abstained during previous parliamentary votes on Italy's military mission in Iraq but Berlusconi and his right-wing allies command a strong majority in the assembly.

"After reading the Red Cross report, it was clear that the use of torture in Iraq was systematic," Rutelli said to explain his coalition's change of heart about Italian troops in Iraq.

"Bush's defence of (US Defence Secretary Donald) Rumsfeld and Berlusconi's embarrassed declaration yesterday was a turning point that forced us to act."

In his statement on Monday, Berlusconi condemned the abuse and called for "exemplary punishments" to be meted out "at all levels" for those responsible.

"I am deeply distressed by the humiliation and suffering inflicted by certain US soldiers on certain Iraqi prisoners," he said.

And his minister for European affairs, Rocco Buttiglione, said the leaders of the US forces in Iraq should resign over the affair.

Berlusconi's right-wing government is expected to face a grilling in parliament on Wednesday over the situation in Iraq.

Italian opposition leaders called on Monday for Bush's visit to Rome to be cancelled as a protest against the prison scandal.

"The Italian government would do well to cancel the events of June 4 with Bush, as long as full light has not been shed on the torture affair," said Green Party leader Alfonso Pecoraro Scanio.

If Bush's visit goes ahead, the US president can expect to be greeted by mass demonstrations organised by an alliance of anti-globalisation groups, the Greens and the Communists.

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