The top U.S. military officer says the Pentagon is beginning to consider ways to bring the Sunni Arab tribes of Iraq's Anbar province more fully into the battle against the Islamic State group.

The chairman of the Joint Chiefs of Staff, Gen. Martin Dempsey, told reporters Thursday that empowering the tribes is one of three key elements of a strategy for rolling back IS fighters in northern and western Iraq.

The other elements are advising and assisting Iraqi government troops and creating so-called national guard units as a sort of quasi-military force that must first gain legal approval from the Iraqi government.

Enlisting the help of Anbar's tribes was critical to the success of U.S. efforts to stabilize Iraq in the latter stages of the Iraq war in 2007-2008.