The Obama administration has been “vacillating” on its request that lawmakers grant the president additional war powers to combat the Islamic State, leaving congressional Democrats frustrated and both the House and Senate poised to adjourn this year without passing any legislation, even as the conflict in the Middle East escalates.

The Senate Foreign Relations Committee had to abruptly cancel a hearing on the Islamic State scheduled for Tuesday after its star witness, believed to be Secretary of State John Kerry, said he could not attend.