Updated

Italy and the United States said Friday they had failed to agree on the circumstances surrounding the death of an Italian intelligence agent killed by U.S. soldiers in Iraq, saying they couldn't reach any "shared final conclusions."

The two governments issued a joint statement on the investigation into the March 4 death of agent Nicola Calipari (search), who was killed after securing the release of an Italian hostage who had been held by Iraqi militants. U.S. soldiers fired on the Italians' vehicle as it approached a U.S. checkpoint near Baghdad's airport.

It said the investigation into the shooting had been concluded, and that the two countries would 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 over a month on the joint investigation in the killing, which sparked outrage in Italy and put increasing pressure on Premier Silvio Berlusconi (search) to withdraw Italy's estimated 3,000-strong contingent from the country.

But from the start, testimony from the two survivors of the shooting clashed with the U.S. military's account.

The Americans maintain that soldiers fired warning shots in the air, then shot at the engine block because the car was speeding. The ex-hostage, journalist Giuliana Sgrena (search), and another intelligence agent who was driving the car insist they saw the beam of a warning light virtually at the same time gunfire broke out. The agent has also testified he was driving slowly.

"Out of a dutiful homage to Calipari, and out of an indispensable national 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 (search) told reporters after the statement was released.

The incident strained relations between the two allies, and Berlusconi made clear as recently as Thursday that he wouldn't sign off on any joint finding unless Italy was convinced of the conclusions.

However, the statement tried to smooth over the differences.

"The alliance between Italy and the United States remains firm and there is a strong and solid friendship between the two countries based on shared values," the statement said. "Such values require us to remain by the side of the Iraqi people ... to contribute to the reconstruction of a stable, democratic and safe Iraq."

Berlusconi said Friday he was willing to discuss the matter in Parliament, where he will hear mounting calls from leftist politicians for Italy to pull its troops from Iraq.

"The rupture between the United States and Italy is not just bureaucratic but political: Berlusconi's government should realize that and pull its soldiers from Iraq," Greens lawmaker Paolo Cento (search) was quoted as saying by the ANSA news agency.

Calipari, hailed at home as a hero, died while trying to shield Sgrena from the gunfire.

In the eight-point statement, the two countries called Calipari an "extraordinary man" who gave his life for Italy and was "an esteemed friend of the United States."

Fini said the final report would be released "within a few days," and that it would make clear "why the Italian government could not sign off a reconstruction of events that in our opinion does not capture 100 percent what happened."

Berlusconi had put his government's prestige on the line with assurances to the nation that full light would be shed on the shooting. The war in Iraq was highly unpopular among Italians, who also opposed the deployment of Italian troops in Iraq to help reconstruction.

Pressure on Berlusconi's coalition grew after news reports suggested the final report into the killing would exonerate the U.S. soldiers. The soldiers had been on high alert at the time because the U.S. ambassador, John Negroponte, had been due to pass by the checkpoint.

Italian prosecutors have launched a criminal probe into the killing. On Tuesday, the bullet-riddled Toyota Corolla involved in the shooting was flown to the Pratica di Mare air base near Rome after repeated requests by Italian prosecutors to inspect it.

"Within our respective systems, we will try to establish the facts, to establish the truth, and to establish responsibility," Fini said, adding that the Italian judiciary probe would "do what's in its power."

Fini said Italy had a relationship with the United States "that continues to be amicable and one of sincere cooperation with the U.S. authorities."

Fini said the investigators had one duty: "to reconstruct the facts, to establish the truth and to honor a hero like Calipari."

"It must also be said that there have been many elements on which there have been full convergence in reconstructing the events, over the scenarios in which that tragic event took place," Fini said.