A U.N. team met with Iraqi leaders Sunday to discuss the feasibility of early legislative elections, and its leader pledged to do "everything possible" to help the country regain its sovereignty.

Meanwhile, insurgents attacked U.S. Army convoys with a roadside bomb and a grenade in two cities Sunday, injuring at least three soldiers, witnesses said. A bomb planted inside a police station killed three policemen and injured 11 others on Saturday, officials said.

The United Nations team held talks for about two hours with members of the U.S.-appointed Governing Council at the start of its mission to break the impasse between the United States and the country's influential Shiite Muslim clergy on the blueprint for transferring sovereignty to the Iraqis.

"The U.N. can only emphasize its wish to do everything possible to help the Iraqi people with all their sects and components to come out from their long plight and to help them regain independence and sovereignty," said Lakhdar Brahimi (search), Secretary-General Kofi Annan's special adviser on Iraq.

In the latest violence, a U.S. convoy was hit by a rocket-propelled grenade in the northern city of Mosul on Sunday, wounding one soldier, witnesses said. A U.S. military official in Mosul, however, said the car was damaged in a road accident and would not comment on injuries.

Also Sunday, a roadside bomb exploded near an Army convoy in Fallujah (search), west of Baghdad, injuring two soldiers, witnesses said. The U.S. command in Baghdad did not confirm the incident.

On Saturday, a bomb exploded inside a police station, killing three policemen and injuring 11 others, in Suwayrah, 30 miles south of Baghdad, police Lt. Odai Salman Abed (searchsaid Sunday.

The U.N. team, which arrived Saturday, includes an election expert, Carina Perelli of Uruguay. Annan said in a statement Saturday that the U.N. experts would hold "intensive consultations" with Iraqi leaders and members of the U.S.-led coalition and listen to the views of all Iraqi constituencies.

"I hope the work of this team will help resolve the impasse over the transitional political process leading to the establishment of a provisional government for Iraq," Annan said.

He did not say how long the team would remain in Iraq. However, a senior Iraqi official, speaking on condition of anonymity, said members would stay for about 10 days.

They were expected to travel to the Shiite holy city of Najaf to meet Grand Ayatollah Ali al-Husseini al-Sistani, whose demand for early elections threatens to torpedo U.S. plans for transferring power to Iraqis by July 1.

Al-Sistani insists that the new legislature be elected, while the Americans want the members appointed in 18 regional caucuses. The legislature will choose a new sovereign government that will take office by July 1.

Ahmad Chalabi, a Westernized Shiite politician with close Pentagon links, met in Najaf with al-Sistani for about 90 minutes.

Chalabi, who is also a member of the Governing Council, told reporters he was confident that the U.N. team would be persuaded that early elections were possible.

"We will tell the U.N. delegation that an election is possible. We reject any delay in the transfer of powers to Iraqis," he said, adding that Washington should stick to the July 1 deadline.

Although the Shiites are pressing for an early ballot, many leading Sunni Muslims fear an election under U.S. occupation would produce a government dominated by majority Shiites, who were suppressed for generations by Iraq's Sunni Arab minority.

The Sunni Muslim president of the Iraqi Governing Council, Mohsen Abdel-Hamid, told reporters that the council and the U.N. team "discussed all forms of an election that are adequate to bring about a representative government keeping in mind that there's no delay to the June 30 deadline."

He had told reporters Saturday that the U.N. team's findings would not be binding on Iraq's leadership.

Failure to resolve the impasse with al-Sistani would throw the Bush administration's Iraq policies into disarray during an election year and could stoke sectarian tensions in a country already ravaged by terrorism and an insurgency.