Berlusconi told parliament on Thursday that Italy will not allow the incident to affect its relations with the United States.
"Our position and expectations were formulated on March 8: Shed light on the circumstances of the death of Nicola Calipari, identify those responsible and call for the guilty to be punished," he said.
He reiterated Italy's view that US soldiers must shoulder some blame but stopped short of explicitly demanding an apology from the United States, as wanted by the opposition.
Berlusconi reaffirmed that "friendly ties between Italy and the United States cannot be called into question".
"And I want to dispel any possible confusion: There is no link between the killing of Calipari and our country's mission in Iraq," he added.
"Friendly ties between Italy and the United States cannot be called into question"
Italian prime minister
Any withdrawal of Italy's 3000 troops from Iraq will be done "uniquely in consultation" with the allies, he said.
"The withdrawal of troops will be gradual and will take place when the situation in Iraq has normalised," he added.
Parliament voted in March to extend the mission in Iraq for another six months, and Berlusconi has said Italy could begin pulling out troops in September, if Italy's allies agreed.