WASHINGTON, United States (AFP) — The United States gathered its allies in the coalition fighting the Islamic State group yesterday and agreed on a plan to corner the jihadists in their final bastions.

US Defence Secretary Ashton Carter told reporters that an accelerated military effort would soon see the group pushed back to Raqa in Syria and Mosul in Iraq.

And US officials said donor countries had pledged a total of $2 billion towards the cost of rebuilding Iraq and insulating its communities from extremism.

But Carter warned that isolating and taking out what he called the IS “parent tumour” would not eliminate its ability to spring or inspire attacks elsewhere.

And, as if on cue, IS propagandists released a video claiming last week’s truck attack in Nice that left 84 dead, and threatening more against coalition states.

Defence ministers from the Western and Arab countries of the coalition said they 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 air base outside Washington.

The Pentagon chief did not reveal details, but added: “Let me be clear: They culminate in the collapse of ISIL’s control over the cities of Mosul and Raqa.”

Britain’s defence minister, Michael Fallon, said London would double to 500 the number of its troops assigned to train Iraqi and Kurdish forces fighting the IS group.