US Pentagon chief vows 'lasting defeat' against Islamic State

Only days after taking office, Carter convened the extraordinary meeting of more than two dozen senior military officers, ambassadors and intelligence officials at the sprawling US Army base of Camp Arifjan.

Speaking to American troops at the base before the talks, Carter said the US-led coalition was "pressing" the IS group "very ably from Kuwait and elsewhere".

"And we will deliver lasting defeat, make no doubt," he said.

Carter said he had called the meeting of commanders and officials "to sit around one table and talk about all of the dimensions of this campaign".

The discussion would look not just at the fight in Iraq and Syria, where US and coalition aircraft have carried out daily bombing raids, but the wider regional struggle against IS, he said.

"ISIL is not just a threat to Iraq and Syria. It's a larger threat to the region," said Carter, using an alternative acronym for the Sunni extremist group.

Asked by one soldier if Washington would consider sending ground troops to take on the jihadists, Carter said any additional military action would have to be weighed carefully.

But he added "we'll do what it takes" to prevail.

President Barack Obama, anxious to avoid a drawn-out ground war, has backed an air campaign but ruled out deploying "boots on the ground".

The talks follow more than six months of US-led air strikes that have halted IS advances for the most part and enabled Kurdish forces to recapture some ground in northern Iraq and the Syrian town of Kobane on the border with Turkey.

But the jihadists still hold large swathes of territory seized last year across Iraq and Syria and appear to have spread their influence to Libya.

In recent days, IS has claimed responsibility for bombings in Libya as well as the murder of 21 Coptic Christians, most of them Egyptian.

Recruiting Sunnis to fight

The meeting of top brass and diplomats was not intended to produce a new strategy but to allow Carter to better understand the challenge posed by the jihadists and the range of efforts aimed at defeating them, said a senior US defence official.

Carter would be looking for an update on the Iraqi government's efforts to recruit other Sunnis into the fight against IS, the official told reporters.

Carter, an experienced Pentagon technocrat who took office last week, "wants it to be an open conversation regardless of rank," without formal presentations featuring power point slides, the official said.

Commanders believe the air war against IS and the training of Iraqi soldiers is mostly on course, but Baghdad's Shiite-led government has more work to do to persuade Sunnis to take up arms.

"On the military side, things are going well," the official said, adding however that "it's still yet to be seen how the Iraqis are really going to lead this thing."

"Thousands" of Sunni tribesmen have signed up to fight but a proposed Sunni national guard was still a long way off, the official said.

"Are Sunnis in the fight? Yes. Are they in the numbers we want? No.