President Bush called Premier Silvio Berlusconi (search) on Wednesday to express his regret for the March killing of an Italian agent by U.S. troops in Iraq. The call came days after Washington and Rome issued rival reports about the shooting death.

Berlusconi's office described the conversation as "long and cordial" and said the two countries reaffirmed their commitment in Iraq. Berlusconi, a staunch ally of the United States, sent about 3,000 troops in Iraq after the ouster of Saddam Hussein (search).

But the March 4 death of Nicola Calipari (search), hailed as a hero in Italy, has caused friction between Washington and Rome, and Berlusconi's government has come under pressure to reevaluate the Italian troop deployment in Iraq.

White House spokesman Scott McClellan said Bush reiterated regret over "the tragic accidental death" of Calipari and called him a hero.

"The two leaders agreed that the tragedy would not harm the strong friendship between the United States and Italy nor our commitment to help the Iraqi people build a brighter better future," McClellan said.

Berlusconi's office said Bush asked the premier "to speak to Calipari's family to renew the feelings of affection and sharing for the death of someone dear to them."

"The two countries remain united in their commitment in favor of the Iraqi people and government for the reconstruction of an Iraq that is stable, free and democratic," said a statement from Berlusconi's office.

Calipari was mistakenly killed by U.S. soldiers at a checkpoint near Baghdad airport. He had just secured the release of Italian journalist Giuliana Sgrena (search), who had been in the hands of her abductors for a month. Sgrena and another intelligence agent in the vehicle were wounded.

After a joint investigation, Italian investigators and the U.S. military differed over aspects of the shooting and issued separate conclusions.

The U.S. report cleared the soldiers of any blame, while the Italians said the troops' fatigue and inexperience played a role in the shooting.

Berlusconi is scheduled to address parliament on the shooting Thursday.

Italian investigators found no evidence Calipari was deliberately killed, and their report did not object to many of the findings of fact contained in the American report. Still, they refused to sign off on the U.S. conclusion that the soldiers bore no blame.

Rome prosecutors are conducting their own investigation into the case.