A U.S. military investigation into the shooting death of an Italian intelligence officer in Baghdad (search) is expected to conclude that American soldiers generally followed instructions as they fired on an approaching car, a senior U.S. defense official said Monday.

However, the probe into the March 4 shooting is expected to raise questions about the rules of engagement given to U.S. soldiers manning checkpoints in Iraq, said the official, who spoke on the condition of anonymity because the report had not been finished. These instructions include descriptions of how much force U.S. soldiers are allowed to use against potential threats.

While Italian officials participated in the U.S. investigation, it was unclear whether the Italians would endorse the report, the official said.

News reports in Italy said the Italians disagreed with the findings, but a U.S. Embassy spokesman in Rome (search), Ben Duffy, said, "We are still hoping for a combined report."

The Italian officer, Nicola Calipari, was killed March 4 when U.S. soldiers fired on a car carrying him and two others as it approached the American checkpoint. He died trying to shield a freed Italian hostage, Giuliana Sgrena (search), whom he had helped release from her insurgent captors.

From the first hours after the shooting, Rome and Washington have differed over what led to the killing.

The U.S. official left open whether the soldiers involved in the shooting could face specific criticisms of their performance. A conclusion that they followed their orders, however, could make it less likely they would be accused of having committed major errors.