The spiritual leader of Iraq's Shiite majority Saturday called on bickering politicians in the clergy-backed United Iraqi Alliance (search) to set aside differences and form a government more than a month after landmark elections.

The U.S. military said it launched an "aggressive" investigation into the shooting at an American checkpoint that killed an Italian intelligence agent, who died in the arms of an Italian journalist that had just been freed after a month as a hostage of Iraqi insurgents.

Giuliana Sgrena (search), 56, injured in the shooting near Baghdad airport, flew home to freedom Saturday after spending the night in a U.S. military hospital.

A roadside bomb killed three Iraqi army soldiers in Baghdad's Bab al-Mu'adam area early Saturday, according to Wisam Muhsin, an official at al-Kindi hospital. Another four soldiers were injured.

Alliance members meeting in central Baghdad agreed to try form a government and convene the 275-member National Assembly by March 15. Iraqis voted for the assembly on Jan. 30 and the alliance has already missed two previous target dates -- March 1 and 6.

Mohammed Bahr al-Ulloum, an alliance deputy, said they agreed the National Assembly would convene "no later than March 15."

Another deputy, Fattah al-Sheik said pressure would be put on interim Prime Minister Ayad Allawi "and the Kurds" so that a cabinet would be ready by that date.

Allawi's party finished third with 40 seats in the assembly, compared to the alliance's 140 and the Kurdish coalition's 75. He has been trying to build his own coalition in an effort to keep his job.

The alliance's decision to set a date came after a Grand Ayatollah Ali al-Sistani demanded that its members stop bickering. Al-Sistani was the guiding force behind the alliance.

Sheik Fawaz al-Jarba, one of the few Sunni Arabs in the alliance, said after meeting al-Sistani in Najaf that the cleric urged the group "to unite and to form the new government as soon as possible and not to delay this issue any longer, and that the interests of Iraq and Iraqis should be their first priority."

The alliance needs a two-thirds majority, or 182 seats, to begin the process of establishing a government and making Ibrahim al-Jaafari prime minister.

"Al-Sistani demanded that we put aside minor matters and that we should be united. I am not comfortable with the delay in holding the assembly," said Mudhar Shawkat, a senior official in Ahmad Chalabi's Iraqi National Congress.

He said failure to convene the assembly "represents an insult to Iraqi voters."

Abbas Hassan Mousa Al-Bayati, head of the alliance's Turkomen bloc, said a parliament speaker would be named on the day the National Assembly convened.

"It seems that the general opinion is leaning toward the parliament speaker being a Sunni Arab and the president being Mr. Talabani," al-Bayati said.

Jalal Talabani, leader of the Patriotic Union of Kurdistan, and one of the two parties in the Kurdish coalition, has long been the Kurds choice for president.

A Sunni Arab speaker would go far toward appeasing the minority, which is thought to make up the core of the insurgency, and like the Kurds makes up about 15 to 20 percent of Iraq's 26 million people. But unlike the Kurds, Sunni Arabs largely stayed away from the election.

Al-Bayati said the candidates would include interim President Ghazi al-Yawer and interim Minister of Industry Hajim al-Hassani.

But the main sticking point in forming a government has been the alliance's inability to broker a deal with the Kurds.

Kurdish leaders have demanded constitutional guarantees for their northern regions, including self-rule and reversal of the "Arabization" of Kirkuk and other northern areas. Saddam relocated Iraqi Arabs to the region in a bid to secure the oil fields there.

Redha Jawad Taqi, a spokesman for the Supreme Council for the Islamic Revolution in Iraq, said "Kurdish demands are negotiable. We can meet them 100 percent if the demands do not affect others, such Arabs and Turkomen. If this is not achievable, then we should look for compromise."

Adnan Mufti, who heads the PUK office in northern Irbil, said talks between Kurdish officials and the head of the alliance, Abdel Aziz al-Hakim, were "positive" and that the Kurds were "optimistic."

In Baghdad, Sgrena left in an Italian government plane and was met at Rome airport by Prime Minister Silvio Berlusconi. She had been abducted in Baghdad on Feb. 4.

Berlusconi, an ally of the United States who has kept Italian troops in Iraq despite public opposition at home, has demanded an explanation from the United States, and in a five-minute conversation with President George W. Bush received assurances that it would.

In Baghdad, U.S. Col. Bob Potter said coalition forces were "aggressively investigating the incident."

About 200 foreigners have been abducted in Iraq in the past year, and more than 30 of the hostages were killed.

Florence Aubenas, a veteran war correspondent for France's leftist daily Liberation, and her interpreter, Hussein Hanoun al-Saadi, were also abducted nearly two months ago.

In other violence, gunmen in two vehicles west of Baghdad, in Abu Ghraib, killed an Iraqi army officer, said Capt. Akram al-Zubaie.

Gunmen killed a Turkish driver and an Iraqi Kurdish official in two separate attacks in this northern city of Mosul on Saturday, witnesses said. Witness Mohammed Jassim Ali said the assailants began shouting afterward, saying they belonged to Al Qaeda in Iraq and that they shot the driver because he was carrying supplies to American troops.