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(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.

In a series of tweets Monday morning, Graham, who sits on the Senate Foreign Relations Committee, said he was working to set up a call with Secretary of State Mike Pompeo to discuss the matter, which he called a “disaster in the making.” Graham also said if the administration continues with the plan, he would introduce a Senate resolution opposing it and asking for a reversal.

“Expect it will receive strong bipartisan support,” he wrote of the possible resolution.

Later on Monday Graham tweeted that he and Democratic Sen. Chris Van Hollen of Maryland will introduce bipartisan sanctions to call for Turkey to be suspended from NATO if it attacks Kurdish forces.

Trump threatens to obliterate ‘Turkey’s economy’

Trump also vowed later on Monday to retaliate against Turkey should the country do anything he “consider(s) to be off limits,” saying in a tweet that he “will totally destroy and obliterate the Economy of Turkey” if that happens.

Following the President’s tweet, Graham again took to Twitter to criticize Trump, writing, “No matter what President Trump is saying about his decision, it is EXACTLY what President Obama did in Iraq with even more disastrous consequences for our national security.”

“Unlike President Obama, I hope President Trump will reassess and take sound military advice,” he wrote.

Earlier this year, Graham was among a broad bipartisan group of Senators that approved a bill that included a provision urging Trump not to precipitously withdraw troops from Afghanistan and Syria until terrorist groups there are destroyed. After Trump announced last December that he was withdrawing US troops from Syria, Graham called the decision a “disaster” and later praised Trump after he announced he would keep some troops in the country.

As of last month, the administration said about 1,000 troops were operating in northeastern Syria. Sunday’s statement did not specify if Trump’s decision constituted a full withdrawal of personnel from the country.

Former US Ambassador to the United Nations Nikki Haley also criticized Trump’s move on Monday, writing in a tweet that “We must always have the backs of our allies,” and that Kurdish forces were “instrumental” to the US’ fight against ISIS in Syria. “Leaving them to die is a big mistake,” Haley wrote.

Responding to the former ambassador, the Syrian Democratic Forces said in its own tweet that “The world relies on strong #American leaders like (Haley)” and that it hopes “our US partners will reverse this decision & not abandon our combined effort in NE Syria. #TurkeyIsNotOurFriend.”

CNN’s Helen Regan and Jeremy Diamond contributed to this report.