WASHINGTON: The Islamic State poses a greater danger than a conventional “terrorist group” and is pursuing a vision that could radically alter the face of the Middle East, US defence leaders said Thursday.

The IS jihadists could be contained and eventually defeated by local forces backed by the United States, but the Sunni population in both Syria and Iraq would need to reject the group, Defence Secretary Chuck Hagel and General Martin Dempsey told reporters.

Hagel warned that the Islamic State is better armed, trained and funded than any recent militant threat.

“They marry ideology and a sophistication of strategic and tactical military prowess. They are tremendously well funded. This is beyond anything we have seen,” Hagel told a news conference.

Dempsey, the chairman of the Joint Chiefs of Staff, said that the group adheres to a fanatical ideology and has “a long-term vision” to take over Lebanon, Israel and Kuwait.

“If they achieve that vision, it would fundamentally alter the face of the Middle East and create a security environment that would certainly threaten us in many ways,” he said.

Hagel said dozens of US air strikes have helped thwart the momentum of the jihadists around the Mosul dam in northern Iraq, helping Kurdish forces counter the militants.

“American air strikes and American arms and assistance helped Iraqi and Kurdish forces blunt ISIL's advance around Arbil, where American diplomats and troops are working, and help the Iraqis retake and hold-Mosul dam,” Hagel said.

The bombing runs and humanitarian aid to the local population have stalled the Islamic State's “momentum and enabled Iraqi and Kurdish forces to regain their footing and take the initiative“.

Asked if the US would hit the militants in neighbouring Syria, Hagel did not rule out that option but did not indicate strikes there were imminent.

Dempsey said the extremists would ultimately have to be taken on in neighbouring Syria, possibly by other more moderate rebel elements.

“Can they be defeated without addressing that part of the organisation that resides in Syria? The answer is no,” the general said.