The top U.S. military officer says Iraq needs to let the United States know now whether American troops should remain in the Middle Eastern country beyond the end of the year.

Joint Chiefs of Staff head Admiral Mike Mullen told reporters before landing in the northern Iraqi city of Mosul Monday that Iraq's indecision is pushing the U.S. to a point where it will be difficult to alter its draw-down plan.

Mullen said U.S. and Iraqi military operations in recent weeks have reduced the surge in violence there, but added he was in a “wait-and-see mode” about whether that progress can be sustained.

U.S. officials have grown increasingly frustrated that Iraqi leaders have not yet announced whether they want U.S. troops to remain in the country beyond a planned December pullout date.

Both Iraqi and U.S. officials have expressed concern about Baghdad's ability to cope with security after the withdrawal.

Fifteen U.S. soldiers were killed in Iraq in June, making it the deadliest month for U.S. military personnel there in two years.

Before Mullen traveled to Iraq, he met with commanders and troops in eastern Afghanistan, where members of the Taliban-allied Haqqani network are attacking U.S. forces.

Mullen said Washington continues to press Islamabad to go after Haqqani militants and members of other groups that have found safe havens in Pakistan.