WASHINGTON - The United States admitted Thursday that the Islamic State is the most dangerous group it has faced in recent years and warned that the Middle East faces a long-term battle to defeat it.
Pentagon chiefs said the jihadist group could be eradicated if local Sunni communities reject it and regional powers unite to fight it, but only if the battle is taken into Syria and not just Iraq.
Speaking after the US military said it had already carried out a failed hostage rescue mission inside Syria, and against the backdrop of new air strikes in Iraq, they warned IS poses a considerable threat.
"They marry ideology and a sophistication of strategic and tactical military prowess," Defence Secretary Chuch Hagel said. "They are tremendously well funded. This is beyond anything we have seen."
General Martin Dempsey, chairman of the Joint Chiefs of Staff, said: "This is an organisation that has an apocalyptic end of days strategic vision that will eventually have to be defeated."
Dempsey warned the jihadist vision of a wider Muslim caliphate could "fundamentally alter the face of the Middle East and create a security environment that would certainly threaten us in many ways."
"Can they be defeated without addressing that part of the organisation that resides in Syria? The answer is no," he said, when asked if the campaign against the group could go beyond Iraq.
He said the fight could not be won by US military prowess alone but only with regional support and that of "the 20 million disenfranchised Sunni that happen to reside between Damascus and Baghdad."
Washington has launched air strikes against IS positions and boosted arms supplies to Kurdish forces, but still wants Baghdad's Shiite-led government to open its arms to Sunni moderates.
The warning came after the IS on Tuesday released a video showing a militant with a British accent beheading American journalist James Foley, and threatening a second US hostage.
The murder has stoked fears in Britain and beyond that the territory the militants have seized in Syria and northern Iraq could become a launching pad for a new round of global terror attacks.
Failed US rescue
In six bombings near a dam north of Mosul, US warplanes damaged three Humvee armored trucks, another vehicle and several roadside bomb "emplacements," according to US Central Command.
The US military said it has conducted 90 air strikes in Iraq since August 8, including the latest raids. Fifty-seven of those operations were to support of Iraqi government forces near the Mosul dam.
Separately, officials confirmed that in recent months, US special forces carried out a raid inside Syria to try to rescue people held hostage by IS militants, reportedly including Foley.
"This operation involved air and ground components and was focused on a particular captor network," Pentagon spokesman Rear Admiral John Kirby said.