Baghdad, Iraq ? A suicide car bomber struck a group of tribal chiefs who opposed al-Qaida, killing at least 18 in a market area near Fallujah. Tuesday’s attack underscored the difficulties facing Sunni leaders in trying to wrest control of Anbar province from the terror network.

Much of the al-Buissa tribe has formed an alliance against al-Qaida in Iraq, which has alienated more moderate Sunnis with its brutality and dependence on foreign fighters. The U.S. military has touted the alliance, the Anbar Salvation Council, as a success in its efforts to stabilize the country.

The bomb exploded in a pickup truck next to where the elders were trying to solve a tribal dispute in Amiriyah, 40 miles west of Baghdad, police said.