ROME — After a five-week joint investigation, U.S. and Italian officials said yesterday they had failed to reach agreement on the circumstances of U.S. troops' fatal shooting of an Italian intelligence agent in Baghdad, Iraq, on March 4. The deadlock keeps alive a dispute that is undermining the standing of Prime Minister Silvio Berlusconi, a key U.S. ally in Iraq.

Italian criminal investigators pressed forward with their own investigation, which includes inspection of the bullet-damaged Toyota Corolla in which agent Nicola Calipari and journalist Giuliana Sgrena were riding when U.S. troops opened fire on them. Sgrena was wounded.

"Respect for the memory of Nicola Calipari, as well as for our national decorum, could only prevent the government of Italy from assenting to a reconstruction of the events that does not correspond with what happened that evening," said Italy's foreign minister, Gianfranco Fini.

U.S. officials have said that the car carrying Calipari and Sgrena sped toward a U.S. checkpoint in the dark and ignored warnings to stop. U.S. troops were not at fault in firing, the U.S. side contends. Sgrena has said the car was moving slowly and was given no chance to stop.

In Washington, officials declined to release the full U.S. findings but said a report would probably be issued soon in Baghdad. Fini said the Italian version would be made public "within a few days."

Berlusconi's failure to obtain an admission of wrongdoing from the Americans has renewed criticism of him. He has stationed 3,000 troops in Iraq but said he hopes to begin a withdrawal in September.

Versions of the shooting provided by U.S. officials in Baghdad and Italian survivors differed sharply. U.S. officials said the car was traveling at high speed and the driver failed to heed warning shots, arm gestures and spotlights meant to signal him to stop.

Yesterday, U.S. officials said that the car failed to slow down until fired on and that Calipari had not notified U.S. authorities of his movements in time to advise the soldiers at the checkpoint.

Calipari was escorting the journalist to Baghdad airport at night after winning her release from kidnappers.