Sen. Lindsey Graham (R., S.C.) on Monday blasted President Donald Trump's decision to withdraw U.S. troops from the northern border of Syria.

Graham called in to Fox and Friends to rebuke Trump for the withdrawal, which will happen in advance of a planned invasion of the region by Turkey.

"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," Graham said. "So to those who think ISIS has been defeated, you will soon see."

Graham, a vocal defender of Trump, went on to say he would do everything he can to sanction Turkey's military and economy if they "step one foot into Syria," adding, "I hope I'm making myself clear how shortsighted and irresponsible this decision is in my view."

"This whole thing with the whistleblowers is a political setup. 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 is not true," Graham said.

Graham isn't the only Republican senator who has spoken out against Trump's foreign policy move. Senate Majority Leader Mitch McConnell (Ky.) on Monday said he urged Trump to "exercise American leadership to keep together our multinational coalition to defeat ISIS and prevent significant conflict between our NATO ally Turkey and our local Syrian counterterrorism partners."

McConnell argued that ISIS and other terrorist organizations "remain dangerous forces in Syria and the ongoing Syrian civil war poses significant security and humanitarian risk."

Sen. Ted Cruz (R., Texas) also blasted the strategy, writing that it would be "DISGRACEFUL if we sat idly by while Turkey slaughters the Kurds."

Trump responded to the backlash during a press conference later in the day, saying he "fully understand[s] both sides" of the issue.

"We want to bring our troops back home and I got elected on that," Trump said. "I fully understand both sides but I promised to bring our troops home."