US military investigators have cleared American soldiers of any wrongdoing over the killing of an Italian agent at a Baghdad checkpoint, an official says.
Calipari threw himself over Sgrena when the bullets hit
Nicola Calipari was killed by US forces as he travelled in a car near Baghdad airport after securing the release of Italian hostage Giuliana Sgrena.
Ms Sgrena, who had been held by Iraqi kidnappers, was hurt in the incident.
The US soldiers were "not culpable" according to the US military report, which Italy has refused to endorse.
A US army official, speaking on condition of anonymity, said the Italian and US authorities still disagree over the speed at which the vehicle approached the checkpoint and how much communication there was between those in the car and the checkpoint guards.
"The United States is ready to release the report but Italy has more questions," the official said.
US military: Car approaches checkpoint at high speed
Troops attempt to tell driver to stop with arm signals, lights and warning shots
Soldiers shoot into engine
Italian government: Italy makes all necessary contacts with the US for safe passage
The driver stops immediately when a light flashes 10m away
At the same time, shots are fired for 10-15 secs into the car
Although Italy's government, led by Prime Minister Silvio Berlusconi, has been a staunch American ally in the conflict in Iraq, the war is deeply unpopular with the Italian people.
A report completely exonerating the soldiers involved in the shooting could therefore prove deeply inflammatory in Italy, and damaging to Mr Berlusconi.
The US military said the car carrying Mr Calipari was speeding as it approached the temporary checkpoint in western Baghdad.
They claimed the soldiers used "hand and arm signals, flashing white lights and firing warning shots" to get the driver to stop.
However, Ms Sgrena, who had been held captive for more than a month, disputed this version of events, saying that the car had not been speeding and that there had been no warning before the troops opened fire.
Hailed as hero
The US military had also said they had no knowledge of the rescue mission, dismissing as "absurd" Ms Sgrena's suggestion that their troops may have deliberately targeted her car.
Sgrena claimed the US soldiers gave no warning
Just after the incident, in an interview with Sky Italia TV, she said it was possible the soldiers had targeted her because Washington opposed the policy of negotiating with kidnappers.
"The soldiers were only complying with the standard operating procedures for those checkpoints, so therefore are not culpable to dereliction of duty [charges]," the US army official told Reuters news agency.
"Everybody feels terrible about it. But given the climate and the security atmosphere, the security procedures at the checkpoint operations have to be run by the letter," he added.
The soldiers involved will face no disciplinary action.
Mr Calipari was fatally shot as he threw himself over Ms Sgrena to protect her from a hail of bullets.
As a result of his action Mr Calipari became a national hero and Italy's leaders joined hundreds of fellow citizens at his funeral.