WASHINGTON (CBSDC/AP) — The chairman of the House Intelligence Committee warns that America is dealing with “the highest threat level we have ever faced in this country.”

Rep. Devin Nunes, R-Calif., told CBS’ “Face the Nation” on Sunday that the threat is coming from the radicalization of young people and foreign fighters heading to Iraq and Syria to join terror groups.

“They’re very good at communicating through separate avenues where it’s very difficult to track,” Nunes said. “That’s why when you get a young person who is willing to get into these chat rooms, go on the Internet and get radicalized, it’s something we are not only unprepared [for], we are also not used to it in this country.”

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Several Americans across the U.S. have been arrested and charged recently with being ISIS sympathizers and trying to join the terror group. Nunes stated “we are having a tough time tracking terrorist cells within the United States.”

“It’s just tough to secure those types of areas if you have someone who wants to blow themselves up or open fire or other threats of that nature and we just don’t know or can track all of the bad guys that are out there today,” he explained to “Face the Nation.”

The U.S. has been conducting airstrikes in Iraq and Syria against ISIS.

The Iraqi military, which was equipped and trained by the United States, has struggled to recover from its collapse a year ago when ISIS militants captured the country’s second largest city, Mosul, and swept over much of northern and western Iraq. Iraqi commanders fled, pleas for more ammunition went unanswered, and in some cases soldiers stripped off their uniforms and ran.

The U.S. is again training Iraqi forces and conducting airstrikes in both Iraq and Syria. The White House announced last week that it was sending up to 450 more U.S. troops to a new base in the Anbar province of western Iraq, mainly to advise the Iraqis on planning and execution of a counteroffensive to retake Ramadi, the provincial capital. More such U.S. hubs could be opened elsewhere in Iraq as the campaign advances.

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Staunch critics in Congress have argued that the current strategy is weak and that it could be strengthened by deploying U.S. troops as spotters for airstrikes. The Pentagon thus far has avoided putting tactical air controllers in the field with Iraqi ground forces and remains opposed to putting U.S. boots on the ground.

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