Updated

The top U.S. commander in the Middle East came under a bold attack Thursday by gunmen in the turbulent Iraqi city of Fallujah. No Americans were hurt, but a local police official said two Iraqis were killed in the shooting.

Also Thursday, a U.N. envoy told Iraq's leading Shiite (search) cleric the world was 100 percent behind his demand for national elections, but there was no sign of agreement on when a vote would be held -- the central issue in Shiite opposition to the U.S. plan for handing over power to Iraqis this summer.

In Fallujah, residents said the Iraqis died as U.S. troops sprayed the area with gunfire after insurgents ambushed Gen. John Abizaid's (search) convoy as it pulled into the headquarters of the Iraqi Civil Defense Corps in the Sunni Triangle city 50 miles west of Baghdad.

Police said the car in which the slain Iraqis were riding was riddled with bullets holes, apparently from a heavy-caliber machine gun.

"We heard from a citizen that someone was killed in a car," Fallujah police Lt. Omar Ali said. "We sent our patrols to the site of the incident. When we arrived there, we saw American forces. They took two dead, put them in a vehicle and left."

One Fallujah man, who would not give his name, said the Americans fired indiscriminately.

"This is a crime that Americans are doing such things to the people," he told Associated Press Television News. "They attack them. This is because they are scared. They just attack indiscriminately."

The attackers fired rocket-propelled grenades and assault rifles from neighboring rooftops and a mosque as Abizaid's convoy pulled into the civil defense headquarters. U.S. troops returned fire, and the convoy pulled away.

A defense official in Washington, speaking on condition of anonymity, said it was likely the insurgents had been tipped off to the presence of the senior general. But Brig. Gen. Mark Kimmitt, deputy operations chief in Baghdad, told journalists he wasn't ready to draw that conclusion.

Insurgents have apparently accelerated attacks against U.S. forces and their Iraqi allies in an effort to wreck the planned June 30 handover of power. Two homicide bombings against Iraqi targets on Tuesday and Wednesday killed up to 100 people. Two American soldiers were killed and another was wounded Wednesday evening by a roadside bomb in Baghdad, the U.S. military said.

A volley of eight mortars was fired Thursday toward a U.S. military base in Baghdad, damaging several cars and lightly wounding three U.S. soldiers, said Kimmitt, the military's deputy operations chief in Baghdad.

Amid the violence, Iraq's U.S. administrators have been trying to overcome criticism of the handover plan from the influential Shiite cleric Grand Ayatollah Ali al-Husseini al-Sistani (search).

The ayatollah demands elections be held to create a provisional legislature, but the United States contends there's no time to properly organize a ballot before the deadline. The U.N. team, which is assessing if elections are possible and examining alternatives, met al-Sistani for two hours at his home in the Shiite holy city of Najaf.

"Al-Sistani is still insisting on the elections," the head of the team, Lakhdar Brahimi, told journalists afterward in Najaf, 90 miles south of Baghdad.

"We are with him 100 percent because elections are the best way to establish a state that serves the interests of its people," he said, adding that al-Sistani and the U.N experts agreed than an election should be "well-prepared."

But Brahimi did not say there was agreement on a timeframe for vote.

In New York, U.N. spokesman Fred Eckhard said the team's discussions since it arrived Sunday have shown a consensus "that direct national elections are the best way" to establish a legitimate government but also that a vote "must be organized in technical, security and political conditions that give the best chance of producing a result that reflects the wishes of the Iraqi electorate."

Eckhard said the issue is when elections can be held.

Al-Sistani has refused to meet with U.S. officials, including the top American administrator, L. Paul Bremer. He has also demanded that an elected legislature approve a temporary constitution still being drawn up, rather than the U.S.-picked Iraqi Governing Council.

The U.S. plan calls for a temporary legislature to be picked by regional "caucuses" so the June 30 transfer can go ahead, then for national elections in early 2005. But al-Sistani has insisted on elections before the transfer.

Support from the 75-year-old cleric is key for the U.S. handover plan, since his rulings are widely respected among Iraq's Shiite Muslim majority. His demands for elections prompted demonstrations by tens of thousands of his supporters last month, forcing Washington to request the U.N. mission.

U.S. officials say they're willing to adjust the caucuses plan but oppose any delay in the handover. Al-Sistani calls the caucuses undemocratic and says it's possible to properly organize a ballot before the deadline. Officials in al-Sistani's office refused to comment on Wednesday's meeting.

The Arab newspaper Al-Hayat cited sources close to al-Sistani saying that if experts feel elections can be properly organized within 10 months, he is willing to delay the handover of sovereignty -- or to carry out just a partial handover -- long enough to allow the vote to take place.

If 10 months were not enough for a fair vote, al-Sistani proposes a system of proposing candidates to be put to a referendum, Al-Hayat said.

The sources said that while al-Sistani was open to U.N. proposals, he had not ruled out issuing a fatwa, or religious ruling, against the American plan if necessary. A fatwa could lead many Shiites to refuse to work with any new government.

Shiites, thought to make up about 60 percent of Iraq's 25 million people, have long been ruled over by Sunnis, who are concentrated mostly in Baghdad and central Iraq, and were harshly suppressed under Saddam Hussein. They are now eager to run the country and would likely dominate elections, raising Sunni concerns.

Sunni supporters of Saddam's ousted regime are thought to be leading the campaign of violence against U.S. troops and Iraqis cooperating with the occupation. Foreign militants also have joined the fight.