Washington (CNN) Sen. Lindsey Graham, one of President Donald Trump's strongest Republican defenders in Congress, blasted Trump Monday over his decision to remove US troops from northern Syria as Turkey plans a military offensive in the region, saying it was "shortsighted and irresponsible."

"This impulsive decision by the President has undone all the gains we've made, thrown the region into further chaos. Iran is licking their chops. And if I'm an ISIS fighter I've got a second lease on life. So to those who think ISIS has been defeated you will soon see," Graham said during an interview on Fox News' "Fox and Friends."

"I hope I'm making myself clear how shortsighted and irresponsible this decision is in my view," the South Carolina Republican added.

Graham, a supporter of the President who has at times previously split with him publicly, said, "I like President Trump. I've tried to help him. This to me is just unnerving to its core to say to the American people, 'ISIS has been destroyed in Syria' -- (that) is not true."

The comments from Graham came hours after the White House made the announcement Sunday night following a phone call between Trump and Turkish President Recep Tayyip Erdogan. The move marks a major shift in US foreign policy and effectively gives Turkey the green light to attack US-backed Kurdish forces. The group, long considered as among Washington's most reliable partners in Syria, has played a key strategic role in the campaign against ISIS in the region.