The top US military officer says Arab countries need to take a more direct role in the US military mission in Iraq before it can be credible and sustainable.

Army Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, said Sunday that President Barack Obama has not yet signed off on a broad military campaign plan against the Islamic State group, in part because of the lack of Arab participation so far.

Obama was briefed on the plan last week.

Dempsey said the plan calls for attacking the Islamic State fighters from several directions at once. That is expected, over time, to help Iraqi ground forces retake territory lost over the past year.

Dempsey spoke to reporters traveling with him from Lithuania to Croatia.