Westerners recruited by the terror group ISIS poses a serious national security threat because they could return and launch strikes within the United States, said former Homeland Security Secretary Michael Chertoff.
The U.S. should not allow "fatigue or complacency or distraction with other issues" to overlook the possibility of an attack, Chertoff told MSNBC's "Morning Joe." He said the danger could be "the worst threat situation since the period after 9/11," and that it was "not the time [for the U.S.] to drop our guard."
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"There have been estimates of several thousand Westerners, including Americans, getting experience and getting indoctrinated [by ISIS]. Some of those folks will come back. And, we ought not to kid ourselves that somehow they're not going to be looking to do some damage in the United States and in the West," Chertoff, who served under former President George W. Bush, said Friday.
In light of the downing of the Malaysian jetliner over eastern Ukraine July 17 and the safety of flying, Chertoff said worrying about attacks on planes at high altitudes was "actually the least of our problems." He explained the larger concerns involved potential attacks in and around airports.
"The focus has to be on the lower altitude aircraft and the safety of the airport itself," he said. "The bigger dangers we face now are attacks on aircraft landing or taking off at a lower level that's within the range of a shoulder-fired surface-to-air missile."
Chertoff said the U.S. and other NATO countries needed to be "resolute" in addressing threats posed by the aggression of Russian President Vladimir Putin. He said Putin was "testing" the U.S. and its relationships with other NATO countries.
"[Putin is] going to continue the pressure," Chertoff said. "I think we need to make sure we send a clear message that there are some red lines that we will not allow him to cross."
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