Congress is uniting in opposition to President Trump’s decision for the United States to stand aside and allow Turkey to attack America’s Kurdish allies in northern Syria.

What began as a trickle of criticism after the surprise White House announcement Sunday night became a flood over the course of Monday, led by leaders of his own party and some of his staunchest supporters in Congress and putting the White House in full damage control mode.

“A precipitous withdrawal of U.S. forces from Syria would only benefit Russia, Iran, and the Assad regime. And it would increase the risk that ISIS and other terrorist groups regroup,” said Senate Majority Leader Mitch McConnell in a statement . “American interests are best served by American leadership, not by retreat or withdrawal.”

Sen. Lindsey Graham, one of the president's most reliable defenders, called Trump’s decision to clear U.S. troops from the border region a “disaster in the making” and said he’s planning to draft legislation that would impose economic sanctions on Turkey if it invades Syria. Because of the strong bipartisan consensus, Graham predicts it will pass with a veto-proof supermajority.

“So this is a big win for Iran and Assad. A big win for ISIS,” Graham said on Fox and Friends. “I will do everything I can to sanction Turkey if they step one foot in northeastern Syria.”

After touting the Turkey planned military offensive as a way to deal with thousands of ISIS fighters now held by America's Kurdish allies, Trump insisted he wasn't siding with Turkish President Recep Tayyip Erdoğan against the Kurds and threatened the NATO ally with economic destruction “if they do anything outside of what we would think is humane.”

“If Turkey does anything that I, in my great and unmatched wisdom, consider to be off limits, I will totally destroy and obliterate the Economy of Turkey (I’ve done before!),” Trump tweeted .

On a conference call for reporters, a senior administration official portrayed the president's move as prudent given that Erdoğan appeared intent on going ahead with his planned offensive, despite U.S. objections.

“The United States not in a position to, and will not be in a position to, fight Turkey over, you know, any actions that it takes with respect to Syria,” the official said. “For anyone to characterize the fact that the president is taking care to make sure that our soldiers, sailors, airmen, and Marines are safe has somehow been a green light for a massacre is irresponsible.”

And the official disputed the idea that by withdrawing U.S. troops, Trump was given tacit approval for the military action. “The president made it very clear, publicly and privately, that the United States does not endorse or support any Turkish operation in northern Syria,” the official said. “We weren't asked to remove the troops. The president made the decision on his own to remove the troops for their own safety from that zone of operations.”

Trump defended his decision at a White House event in the afternoon and again last night as he met with Defense Secretary Mark Esper and the Joint Chiefs of Staff in the Cabinet room.

“I just think that's the right thing,” Trump said, insisting he respected the argument made by critics like McConnell and Graham. “The problem with the other opinion is, when do we leave? When do we leave? We're going to stay there forever?”

“We’ve been in Syria for a long time,” Trump said later, flanked by the uniformed chiefs. “We were down to very few soldiers in Syria. We had 50 in the region that you’re talking about — 50 soldiers — and they’ve been already moved out.”

Asked if his decision was firm, Trump replied, “It’s always a firm decision.”