U.S. Rep. Jason Crow on Monday tore into President Donald Trump’s decision to withdraw U.S. troops from northern Syria, with the Colorado Democrat calling the move “a misguided and catastrophic blow to our national security interests.”

“Not only will this decision further destabilize the region, it will make it more difficult for the United States to recruit allies and partners to defeat terrorist groups like ISIS,” said Crow, D-Aurora, in a joint statement with members of a bipartisan congressional delegation that returned Monday from the Middle East.

The White House announced Sunday night that the United States would not intervene in an anticipated Turkish invasion of northern Syria, triggering complaints that the U.S. was in effect abandoning Kurdish fighters who have fought with American forces against the Islamic State.

“Over and over again, we heard from U.S. and foreign leaders of the danger posed to the United States and our allies if Turkish forces moved into northern Syria, an area protected by our Kurdish allies, the Syrian Defense Forces (SDF),” said the lawmakers in their statement, noting that they met with government, military and diplomatic officials in Turkey, Afghanistan and at the Syria-Jordan border during the six-day trip.

The lawmakers added: “The bottom line is that these Kurdish soldiers are the first line of defense in maintaining the gains we have made against ISIS; if Turkey attacks these Kurdish soldiers, there is a grave risk that the ISIS fighters they guard will escape and return to the battlefield.”

In addition to Crow, the delegation included U.S. Reps. Elise Stefanik, R-N.Y.; Abigail Spanberger, D-Va.; Andy Kim, D-NJ; and Chrissy Houlahan, D-Penn.

Republican and Democratic lawmakers alike reacted with outrage to Trump’s decision, with U.S. Sen. Lindsey Graham of South Carolina, a Republican Trump ally, calling the move a “disaster in the making” and threatening to impose economic sanctions on Turkey if the country invades Syria.

U.S. Sen. Mitt Romney, R-Utah, an occasional Trump critic, said Trump’s “decision to abandon our Kurd allies in the face of an assault by Turkey is a betrayal.”

Trump responded in a tweet by threatening to “totally destroy and obliterate” the Turkish economy if it does “anything that I, in my great and unmatched wisdom, consider to be off limits.”

The president continued: “The U.S. has done far more than anyone could have ever expected, including the capture of 100% of the ISIS Caliphate. It is time now for others in the region, some of great wealth, to protect their own territory. THE USA IS GREAT!”

The Associated Press contributed.