The United States gathered its allies in the coalition fighting the Islamic State group on Wednesday and agreed on a plan to corner the jihadists in their final bastions.

US Defence Secretary Ash Carter told reporters that an accelerated military effort would soon see the group pushed back to Raqa in Syria and Mosul in Iraq. He warned that isolating and taking out what he called the IS 'parent tumor' would not eliminate its violent ideology or its ability to spring attacks elsewhere.

But defense ministers from the Western and Arab countries of the coalition now have a military plan to liberate the cities with local Iraqi and Syrian forces.

"Today, we made the plans and commitments that will help us deliver ISIL the lasting defeat that it deserves," Carter told reporters at an airbase outside Washington. "Let me be clear: They culminate in the collapse of ISIL's control over the cities of Mosul and Raqa."