Pentagon spokesman Army Colonel Steve Warren said on April 13 that the front lines of the territory held by the IS militants had been pushed further south and west in Iraq.

"Iraqi security forces and coalition airpower had “unquestionably inflicted some damage” on IS militants, and the group was “now being slowly pushed back," Warren said.

But the militants still control a wide swath of land stretching from west and south of the northern town of Sinjar down through Mosul and across Baiji, including the oil refinery there, which is still contested.

"In Syria, IS fighters have maintained its influence on the ground, recently losing areas around the town of Kobani on the Turkish border, but gaining ground around the central city of Homs and the capital Damascus," Warren said.