Iraqi political leaders reached a compromise Thursday to include more Sunni Muslim Arabs on the committee responsible for writing the country's new constitution, ending weeks of stalemate and raising hopes that the document can be crafted before the panel's deadline expires in two months.

"The problem is solved and ended. The Sunnis will participate in the process of writing the constitution," said Tariq Hashimi, the secretary general of the Iraqi Islamic Party, a leading Sunni organization.

The U.S. military reported, meanwhile, that a roadside bombing killed five Marines on Wednesday near Ramadi, the second time in less than a week that an explosive device in western Iraq has killed that many Marines. An American sailor serving with the Marines in Ramadi was also killed Wednesday, by gunfire.

On Baghdad's treacherous airport road, a suicide bomber steered a car into an Iraqi police convoy, killing six officers at the scene and wounding 25, the Defense Ministry said; two more officers died soon afterward, according to the Associated Press.

The breakthrough in bringing minority Sunni Arabs into the constitution-writing process bridged a divide between leaders of the 55-member constitution committee. Shiite Muslims, the dominant group on the panel, had offered to add 13 Sunnis to the two already on the committee. Sunni groups had demanded that 25 be added.

Under the compromise, the new panel will include members of the existing committee, 15 additional Sunni Arabs with full voting rights and 10 more Sunnis in an advisory, non-voting role. A member of Iraq's Sabean sect, an ancient religious group, will also be added and allowed to vote.

Adnan Janabi, the head of a subcommittee that has been negotiating for weeks to involve more Sunnis in the process, called the compromise "the best we could reach. It was unanimously agreed upon by both sides."

But Saleh Mutlak, who leads a Sunni coalition known as the National Dialogue Council, said: "We bitterly agreed on the decision. The country is in a critical situation, and if we don't agree, the political process will be delayed."

Iraq's Sunni Arabs, who held the bulk of power in Iraq for centuries, boycotted January's parliamentary elections and hold relatively few seats in the 275-member National Assembly. When the Shiite coalition that holds a majority in the assembly formed a constitution committee in May, only two Sunni Arabs were included.

Since then, leaders from across Iraq have been working to ensure that more Sunni Arabs have a role in writing the constitution, which is scheduled to be completed by Aug. 15. The committee could extend the process by six months, but that would delay a referendum on it scheduled for Oct. 15 and ultimately postpone the election of a permanent government.

Party leaders said Thursday that they would assemble a list of candidates' names to be presented to the National Assembly for inclusion on the new panel. Hashimi, the secretary general, said that the list would include members of established parties and independents and that it would be compiled by Saturday.

The deaths of the six U.S. service members near Ramadi added to a sharp increase in U.S. casualties in Anbar province, a vast area that stretches from Baghdad's western edge to the country's borders with Syria, Jordan and Saudi Arabia. Ramadi, the provincial capital, has been a center of Iraq's insurgency for more than a year; insurgent activity in nearby Fallujah led to two U.S.-led assaults on the city, the most recent in November.

Air Force Brig. Gen. Donald Alston, the chief spokesman for the U.S.-led military force in Iraq, said Thursday that he "would not consider the situation in Ramadi to be anything extraordinary at this time."

"The security and the situation in the al-Anbar province has been a challenge for some time," Alston said at a news conference in Baghdad. Acknowledging that "we have an adaptive enemy that can learn," he said the military was investigating Wednesday's roadside bombing, as well as one that killed five Marines on June 9 and other attacks, to determine whether there had been "a change of tactics."

Alston announced that multinational forces in the northern city of Mosul had apprehended a key member of al Qaeda in Iraq, the insurgent group led by Abu Musab Zarqawi, a Jordanian. Mohammed Khalaf, known as Abu Talha, was captured Tuesday without a fight, though he had vowed not to be taken alive and was known to wear an explosive vest at all times, Alston said.

The arrest was made possible by tips from local residents, Alston said. Since Zarqawi declared in May that it was permissible to kill civilians in attacks against security forces, Alston said, "we are getting reporting that cells, as part of his network, are concerned about the consequence of this behavior and the consequence of what they've done to the Iraqi people. The Iraqi people increasingly are exposing the insurgents."

Special correspondent Naseer Nouri contributed to this report.

Gunmen block a mosque in Ramadi, in western Iraq, where officials and tribal elders were due to select representatives to meet with occupation forces.