Despite being an ally of the United States, Rome also criticised the US military for failing to establish rules for checkpoints in Iraq.
In a 52-page report on the "friendly fire" incident, Italy said the shooting of Calipari was not intentional, but it took issue with US findings released at the weekend that exonerated US troops.
Calipari was shot by US soldiers on the night of 4 March as he was escorting freed hostage Giuliana Sgrena to Baghdad airport.
The US inquiry into the incident, in which Sgrena and another Italian secret service agent were wounded, determined it was a "tragic accident" and that US forces followed correct procedures.
Calipari died while escorting
Giuliana Sgrena to the airport
Italy sat on the same inquiry, but refused to sign on to the US conclusions and instead issued its own findings in which it accused US troops of failing to set up "the most elementary precautions" to warn drivers of the approaching checkpoint.
"The attention with which the roadblock was planned and organised was careless to say the least," the report said.
It also denied there were communication problems between the Italians and the US forces before the shooting.
"It is likely that tension ... inexperience and stress led some of the US troops to react instinctively and with little control," the Italians said.
The dispute has strained ties between Rome and Washington, prompting calls in Italy for Prime Minister Silvio Berlusconi to withdraw 3000 Italian troops deployed in Iraq.
Berlusconi is being pressured to
withdraw Italian troops
The US report put much of the blame on Italy for the fatal shooting, saying Italian agents had failed to communicate to US officials their plans to take Sgrena to the airport.
Rome denied that, saying US authorities were "indisputably" aware of the presence of Calipari and a second Italian agent in Baghdad even if "it is likely that they were not aware of the details of their mission".
It added that the Italian agents were not under any obligation to inform the US military about their journey to the airport, but said the roadblock should have adequate signals to give drivers a chance to slow down.
The Italian report condemned the US military for failing to lay down precise rules for its checkpoints, saying this had added to the confusion.
"The lack of formal reference points within clear rules, which could and should have been observed, makes it difficult to identify precisely ... individual responsibilities," it added.
The seven US reservists involved had been warned of attacks in the area and were forced to stay in an exposed temporary roadblock position for much longer than was necessary or normal because of a lapse in US communications.
"It is likely that tension ... inexperience and stress led some of the US troops to react instinctively and with little control"
When the Italian car approached, the soldier first flashed a spotlight at it, then had to fire warning shots and finally lethal rounds, all within seconds, the US report said.
The Italians said the soldier had been given far too many tasks.
"He said he felt threatened by the approaching car, to have thought about his daughters and was literally overwhelmed by actions that needed to be performed in very little time," the report said.
The report also criticised US forces for removing forensic evidence from the scene of the shooting, making it impossible to reconstruct the precise chain of events.