The senior U.S. official said that the forces will be stationed in northern Syria and working alongside groups with a proven track record of fighting ISIS. The move will be described as a “shift” but not a “change” in U.S. strategy against ISIS, the official added.

That could include Kurdish force and allied groups who have come together under the umbrella of the “Syrian Democratic Forces,” according to the official, who spoke on condition of anonymity because the announcement was not yet public.

Obama and his administration have come under mounting pressure amid signs the anti-ISIS coalition has stalled or at least failed to turn the tide against the militants — including the recent Pentagon decision to abandon a failed program to train and equip Syrian rebels.