It said the investigation into the shooting had been concluded and the two countries will now refer the case to their respective national authorities. Italy has launched its own criminal inquiry into the death.
''The investigators were unable to reach shared final conclusions, but after having jointly examined the evidence, they did agree on facts, deductions and numerous problematic recommendations," the statement said.
Italy and the United States had worked for a month on the joint investigation in the killing, which sparked outrage in Italy and put increasing pressure on Premier Silvio Berlusconi to withdraw Italy's estimated 3,000-strong contingent from Iraq.
But from the start, testimony from the two survivors of the shooting clashed with the US military's account.
''Out of a dutiful homage to Calipari and . . . dignity that a government must have, the Italian government could not have been asked to sign off on reconstruction of the facts that as far as we know does not correspond to what happened that night," Foreign Minister Gianfranco Fini said.
The Americans maintain that soldiers fired warning shots in the air, then shot at the engine block because the car was speeding.
