Rescue teams, security personnel, Iraqi police in front of the damaged hotel near security checkpoint, where blast killed or injured dozens

Sunni Arab members of a committee drafting Iraq's constitution have ended a six-day boycott. The return of the members has renewed hopes the charter could be submitted to the Iraqi National Assembly by the August 15 deadline.

Six of the 12 Sunni Arab members who walked out last week attended the latest constitution committee session and the rest promised to return Tuesday.

The Sunnis suspended participation to protest the July 19 murders of two colleagues they say were given inadequate security. The Sunni committee members refused to return to work until the Iraqi government gave them better protection, a greater role in deliberations, and an agreement to launch an international investigation into the assassinations.

U.S. Ambassador to Iraq Zalmay Khalilzad outlined the deal the Sunni members accepted.

"The government has agreed to provide security for the members, to treat them in the same way as members of the T.N.A. [Transitional National Assembly]. They have agreed to an independent investigation under the judiciary. They have agreed that family members or political groupings associated with the people who were killed can participate in the investigation that will take place under the judiciary, and they have agreed that the judiciary can ask for external assistance for the investigation. We have said that, if we are asked to assist in the process, we will look at that," said Mr. Khalilzad.

As the August 15 deadline for the draft constitution approaches, Mr. Khalilzad, who began his job on Saturday, has been intensely engaged in talks to inject new momentum into the drafting process.

The 71-member committee, made up of legislators and politicians representing Shi'ite, Sunni, Kurdish, Christian, and other groups, are said to be still quarreling over several points, including how to share power and resources.

If the committee feels it will miss the deadline, it could ask the National Assembly for a six-month extension. But the U.S. ambassador says reaching a compromise is critical.

"That is important, in terms of weakening the insurgency, winning over the population away from al-Qaida and other foreign terrorists who come here to kill and maim and use Iraqis as cannon fodder for their larger agenda," he added. "They do not give a damn about Iraq or the Iraqis."

Inside the heavily-guarded Green Zone of Baghdad, Australian Prime Minister John Howard paid a surprise visit to Iraqi Prime Minister Ibrahim al-Jaafari. The two leaders said their talks focused on training Iraqi security forces and efforts to improve Iraq's economy.

Australia has been among the strongest supporters of the U.S.-led mission in Iraq, and Mr. Howard wanted to visit some of the 750 Australian troops deployed here.

Meanwhile, suicide bombers continued their strikes on targets in the capital. Monday's attacks followed Sunday's devastating suicide bombing in which a truck packed with more than 220 kilograms of explosives killed dozens of Iraqi civilians near a Baghdad police station.