U.S. Defense Secretary Chuck Hagel
U.S. Defense Secretary Chuck HagelReuters

U.S. Defense Secretary Chuck Hagel said on Thursday that the Islamic State (IS, formerly ISIS) terrorist group poses an “imminent threat” to the United States and may take years to defeat.

“They are an imminent threat to every interest we have, whether it’s in Iraq or anywhere else,” Hagel said at a Pentagon news conference, according to the Bloomberg news agency.

The beheading by Islamic State of American journalist James Foley, shown in a graphic video released this week, has drawn fresh attention and international condemnation to the terrorist group that has seized a swath of Syria and Iraq in its quest to create a Sunni caliphate.

Islamic State “is as sophisticated and well-funded as any group that we have seen,” Hagel said.

“They’re beyond just a terrorist group. They marry ideology, a sophistication of strategic and tactical military prowess. They are tremendously well funded,” he added.

Hagel said U.S. airstrikes in Iraq “have stalled” the group’s “momentum and enabled Iraqi and Kurdish forces to regain their footing and take the initiative.”

Appearing alongside Hagel, Army General Martin Dempsey, chairman of the Joint Chiefs of Staff, said Islamic State “will only truly be defeated when it’s rejected by the 20 million disenfranchised Sunni that happen to reside between Damascus and Baghdad.”

Dempsey said that means the group also will have to be taken on in Syria, where the Obama administration opposes both the group and the regime of President Bashar al-Assad that it’s working to topple. The administration backs what it calls moderate opposition forces that have been overshadowed by militants.

“Can they be defeated without addressing that part of their organization which resides in Syria?” Dempsey said. “The answer is no. That will have to be addressed on both sides of what is essentially at this point a nonexistent border.”

U.S. President Barack Obama recently authorized "limited airstrikes" following threats of an impending genocide committed by IS against the local Yazidi people.

Obama has said the U.S. would not put combat troops on the ground in Iraq and that the targets for airstrikes would be expanded only after an inclusive government is in place.

Earlier this week, IS threatened to attack Americans "in any place" if U.S. airstrikes in Iraq hit its people.

A video published by the group featured a statement which said in English "we will drown all of you in blood".