US officials say attacks in Iraq are down by 60 percent since June, but have also warned that violence could return if Iraqi political leaders do not make more progress on reconciling warring sects and ethnic groups.

President George W. Bush said he was dissatisfied with progress but defended Iraq's political process, saying despite a deadlock on laws in the Baghdad parliament, communities were moving towards reconciliation at the provincial level.

US forces said the suicide bomber struck a foot patrol near a building where a city council meeting was to be held, killing one soldier and wounding 10. Iraqi police said the building was also being used to recruit volunteers for neighborhood patrols, 13 of whom were killed and 10 wounded.

US forces are paying mostly Sunni Arab men to join neighborhood patrols to fight Sunni al Qaeda militants, a tactic Washington says has helped curb violence. But the patrols have been increasingly targeted, especially in provinces like Diyala where US commanders say al Qaeda has regrouped after being pushed out of other parts of Iraq.

US commanders said they had found a torture chamber in Diyala province with chains on the walls and a battery connected to an iron bed and said it was proof of al Qaeda activity.

In another attack, a car bomb parked outside a liquor store in central Baghdad killed three people and wounded 20.