Kerry on ISIS beheading: 'We are not intimidated'

The U.S. strategy for combatting the Islamic State in Iraq and Syria (ISIS) is "starting to gain traction," Secretary of State John KerryJohn Forbes KerryDem Sen. Markey faces potential primary challenge in Massachusetts Judd Gregg: The dangers of the Bolton Doctrine Rubio asks Barr to investigate Kerry over Iran meetings MORE said Monday.

Speaking a day after the terror network distributed a new video depicting the beheading of U.S. aid worker Peter Kassig, Kerry vowed the United States was "not intimidated" by the group.

"ISIL’s leaders assume that the world would be too intimidated to oppose them," Kerry told the Transformational Trends Strategic Forum, using an alternative abbreviation for the group. "Well, let us be clear: We are not intimidated."

Kerry said that diplomatically, the US. had been successful in soliciting "solidarity and help" from partner nations across the globe.

"ISIL is a coalition multiplier," he said. "Governments that can’t agree on almost anything else agree on the imperative of confronting and defeating these terrorists."

Kerry also said the military campaign against the group has "begun to have significant impact."

"The momentum that ISIL built up during the summer has dissipated," Kerry said. "It continues, yes, to commit terrible crimes, but it has also been forced to relinquish bases, abandon training sites, alter its mode of communications, disperse personnel and stop the use of large convoys."

Kerry also hinted that Iraqi security forces were preparing to launch a counteroffensive in the coming months that could reverse gains made by the group.

Still, Kerry acknowledged that much of the world had been galvanized against ISIS because they posed an "unacceptable danger."

"Unlike some extremist groups, it is relatively well-organized — disciplined, even," Kerry said. "Its actions are systemic and planned."

The top U.S. diplomat added that regional instability contributed to concerns over the group's power.

"It is a foe we take very seriously, in part because the dysfunction of some governments in the region has enabled these killers to seize control of more land and more resources than al-Qaeda ever had on the best day of its existence," he said.

The comments from Kerry came as French authorities announced they had reason to believe one of their citizens had appeared in the propaganda video showing the death of Kassig. The group continues to hold other Western hostages, including a 26-year-old American woman.