Italian Premier Silvio Berlusconi (search) suggested Thursday that U.S. soldiers were negligent in the shooting death of an Italian agent in Iraq, but insisted that the slaying wouldn't affect relations with Washington or Italy's troop commitment in Iraq.

In frank remarks to Parliament, the premier rejected calls by extreme left-wing lawmakers for an immediate pullout of Italy's 3,000-strong contingent.

He said a "gradual withdrawal" was on the horizon, but reiterated statements weeks earlier that a pullout would depend on security conditions and agreement with other allies in the U.S.-led coalition.

"There is no motivation to declare today 'everybody home,' which would seem not only irresponsible but incomprehensible," Berlusconi told lawmakers.

Last week, U.S. military investigators cleared American soldiers of any blame in the March 4 death of Nicola Calipari (search).

Berlusconi's speech was a balancing act designed to acknowledge stark differences with Washington over the episode but also to affirm that the "the friendship of the United States toward Italy isn't up for discussion."

Calipari, a veteran intelligence agent, was killed by U.S. soldiers as he was escorting journalist Giuliana Sgrena (search) to Baghdad's airport soon after he had secured her release from Iraqi captors. U.S. soldiers manning a temporary checkpoint fired on the car they were riding in as they approached Baghdad airport.

In its report on the shooting, the American military said the car was speeding, didn't heed warning lights and shots and said better communication between the Italians and the Americans could have prevented the accident.

The Italian investigators on the same probe criticized the Americans for failing to put up signs on the road signaling a checkpoint was ahead and said stress, inexperience and fatigue on the part of the Americans played a role in the shooting.

The Italians concluded Calipari wasn't deliberately killed. But in the most critical point of his speech, Berlusconi said that didn't mean no one was to blame.

"Indeed, the lack of deliberate action doesn't rule out blame attributable to negligence, imprudence or even simple incompetence," he told lawmakers.

He said the government was fully backing a criminal investigation into the death being conducted by Rome prosecutors, and that it remained committed to finding the truth "and possible responsibilities" for the death.

Nevertheless, he stressed that Italy's friendship with Washington would weather the dispute. Citing America's role in liberating Italy during World War II, he said Italy was now committed to working "side by side" with U.S. forces in Iraq and "against the threat of totalitarianism in the new millennium."

Piero Fassino, speaking for the center-left opposition, largely shared Berlusconi's assessment that the incident shouldn't harm U.S.-Italian relations. But he called for the government to take steps to "prepare for the return of troops from Iraq."

A former seven-time premier, Giulio Andreotti, concurred, telling the Senate that the time had come to reflect over the mission's purpose and financing.

Fassino also called for Washington to cooperate with the Rome criminal probe and to issue a formal apology. U.S. President Bush called Berlusconi on Wednesday to express regret over Calipari's slaying, but he didn't apologize.

"Words of friendship have come from the U.S. government, but not an apology for a tragic accident," Fassino said in debate following Berlusconi's remarks. "Those who are responsible would do well in recognizing (their responsibility) and apologize."

Greens leader Alfonso Pecoraro Scanio again demanded the withdrawal of Italian troops and called for the International Court of Justice in the Hague, which resolves disputes between nations, to take up the Calipari case.