An alliance of tribal leaders has worked with US forces against al-Qaeda, resulting in a dramatic drop in violent incidents in the past few months.
In Washington last month, the US commander in Iraq, General David Petraeus, praised tribal leaders, saying they were "helping transform Anbar province and other areas from being assessed as lost as little as six months ago to being relatively heartening".
Baghdad wall shooting
In a separate incident a senior US commander was shot by a sniper as he inspected the construction of a wall surrounding a Sunni Arab enclave in Baghdad, the US military said on Monday.
Colonel Billy Don Farris, a commander in the 82nd Airborne Division, was shot in eastern Adhamiya on May 3, a statement said.
Farris, who was hit by a single bullet, was evacuated from the area and is in stable condition.
The barrier is one of a number being built in Baghdad as part of a three-month-old security plan aimed at halting sectarian violence.