BAGHDAD, Iraq – A suicide bomber detonated a truck packed with explosives outside a Baghdad police station yesterday, killing at least 22 people in the country’s deadliest attack in a week. A separate blast in western Iraq killed a Marine, the American military said.

The attack on the Rashad police station in the eastern neighborhood of Mashtal came during a blinding sandstorm. Security barricades prevented the bomber from reaching the station, but the huge blast destroyed two dozen cars and damaged nearby shops.

Police and hospital officials said 22 people – most of them civilians – were killed and about 30 were injured. The American military, citing initial Iraqi police reports, said 40 people were killed, but police said they were uncertain where that figure came from.

It was the deadliest attack in Iraq since a suicide bomber blew himself up July 16 near a Shiite mosque in the central city of Musayyib, igniting a fuel tanker and killing nearly 100 people.

Elsewhere, gunmen killed the leader of the city council in the insurgent-riddled city of Samarra, 60 miles north of Baghdad, police said. Council chairman Taha al-Hinderah and a companion were gunned down as they walked in the Albu Rahman neighborhood yesterday evening, a police captain, Laith Mohammed, said.

In Mosul, Iraq’s third-largest city, insurgents emptied fuel from two tanker trucks on Al Muthanna Bridge across the Tigris River and set it on fire, police said. Two people were wounded in clashes that followed.

Six policemen also were killed yesterday in scattered attacks in Baghdad and Kirkuk, officials reported. Gunmen in Kirkuk also killed an Iraqi soldier and wounded six people, police said.

The Marine was killed Saturday when a roadside bomb exploded near the desert town of Rutbah, 220 miles west of Baghdad. The American command said the Marine was assigned to Regimental Combat Team-2 of the 2nd Marine Division, but the victim’s name was not released.

Despite the violence, Sunni Arab members of the 71-member committee drafting the new constitution signaled they were about to end their boycott, which began after last week’s assassination of two of their colleagues.

The 12 Sunni Arab members of the committee announced they would meet with the Shiite chairman over breakfast today. A Sunni committee member, Saleh al-Mutlaq, told the Associated Press he and his colleagues had received verbal assurances that their grievances would be addressed.

The Sunnis suspended their participation to protest the assassination of Sunni member Mijbil Issa and adviser Dhamim Hussein al-Obeidi by unknown gunmen. The Sunnis demanded an international investigation into the killings, better security, and a greater Sunni role in deliberations.

Yesterday, members of a bloc of a former prime minister, Ayad Allawi, threatened to walk out in sympathy with the Sunni demands. A committee member, Adnan al-Janabi, who also is part of secular leader Mr. Allawi’s eight-member bloc, criticized the way the commission dealt with the Sunnis.

“Their demands and suspension of membership should have been studied and taken in a way that reassures them and brings them to participate in the draft constitution that we want to be agreed upon by all Iraqis,” he said.

Mr. al-Janabi, who also is a spokesman for Mr. Allawi’s group, said the bloc’s continued participation remains in question.

The mixed makeup of the committee was deemed crucial for drafting a constitution acceptable to all of Iraq’s ethnic and religious communities, a key to any political exit from the unremitting violence and the need for American troops to remain in Iraq.

If Mr. Allawi’s secular group joins the Sunnis in pulling out of the process, it raises the concern that a committee already dominated by Shiite religious parties and ethnic Kurds would be left in control of drafting the charter.

The threatened walkout by Mr. Allawi’s group is the latest hurdle in the commission’s goal of getting a constitution drafted and approved by the assembly August 15. That charter then would be scheduled for a public referendum two months later.