Rome ? Italian investigators have concluded that stress, inexperience and fatigue among U.S. soldiers played a role in the shooting death of an Italian agent in Baghdad, according to a report released Monday.

The probe found no evidence that the March 4 killing of intelligence agent Nicola Calipari was deliberate.

Calipari was killed just after he secured the release of Italian journalist Giuliana Sgrena from Iraqi militants who held her hostage for a month. U.S. soldiers fired on the Italians’ vehicle as it approached the checkpoint near Baghdad’s airport. Sgrena and another Italian agent were wounded.

U.S. investigators, in their report made public Saturday, said the American soldiers gave adequate warning, beaming a light and firing warning shots, as the car traveled on the road toward Baghdad airport. They cleared the U.S. soldiers of any wrongdoing, sparking outrage in Italy, where Calipari had been hailed as a hero.

The two Italian experts who participated in a joint U.S.-Italian probe of the shooting and the government refused to sign off on the American conclusions.

Italy and the United States have publicly differed over crucial points about the incident since the first hours after the shooting.

When several days of negotiations failed to yield a common report, both sides went their own way.

Italy is a main partner in the U.S.-led coalition in Iraq. The approximately 3,000 Italian soldiers sent to Iraq for reconstruction constitute one of the coalition’s largest contingents.

But Premier Silvio Berlusconi, a staunch American ally, has faced political fallout over the case, including calls to bring home Italy’s troops from Iraq.

A journalist looks at the Italian government's Intelligence Web site with the report available for downloading on the death of Italian intelligence agent Nicola Calipari in the Palazzo Chigi premier's office press room, in Rome Monday.

Berlusconi is scheduled to address both houses of parliament on the case Thursday.

The U.S. report contained many blacked-out portions, including the names of the soldiers at the checkpoint and their units. But due to an apparent error, what was blacked out in the report could be read on the Web site of the Italian newspaper La Repubblica.

Some of the material that had been blacked out also discussed training for checkpoint duty and checkpoint procedures.

Mark Allen, a spokesman for the National Guard Bureau, which manages the Army and Air National Guard but has no operational responsibility in Iraq, said he would not comment on any guardsmen’s names published by sources other than the U.S. government.