The conclusions of the report, already rejected by Italian authorities, have soured relations between the two allies and cast a shadow over the future of Italy's military contribution to the US-led coalition in Iraq.
According to the report, released in Baghdad on Saturday, the US soldiers acted under the military rules of engagement on 4 March when a patrol shot at an approaching car that failed to slow down, killing Nicola Calipari, 51, and wounding Giuliana Sgrena, a journalist who had just been released by kidnappers. The Italian car driver was also wounded in the shooting.
"This was a tragic accident and the Multinational Forces-Iraq expresses its deepest sympathies to the Calipari family," said Brigadier General Peter Vangjel, the investigating officer.
A 42-page report - much of it censored - released to the press said the Italians had not informed US authorities they would be driving from the capital to Baghdad airport around 8:50 pm (1650 GMT) after darkness with the released hostage.
Review of procedures
The report, however, recommended a review by the military of procedures it uses at roadblocks. "Spike bars, speed bumps and other traffic calming devices should be used more often at checkpoints," the report suggested.
Communications were also poor that night, the report said. Before the report was issued, a US army officer said US and Italian investigators had disagreed on at least two aspects of the shooting: The speed at which the vehicle approached the US checkpoint and issues related to how or whether the Italian's rescue mission was communicating with US authorities and how communications passed down the chain of command.
Italian MPs want Rome to
withdraw its troops from Iraq
Italy's Foreign Minister Gianfranco Fini said on Friday that a separate inquiry by Italian magistrates would continue after Rome and Washington failed to reach agreement in their joint investigation.
Fini spoke after Italy and the United States issued a joint statement saying that their "investigators did not arrive at shared final conclusions''.
Although the statement underlined Italy's commitment to remain in Iraq, it immediately sparked calls from some Italian lawmakers to withdraw the country's 3300 troops.
"We must now raise our voice and pull out the troops," said Pietro Folena, a communist lawmaker.
The road to the Baghdad airport remains one of the most deadly in the country despite US efforts to secure it.