Rep. Liz Cheney (Wyo.), the No. 3 House Republican, said Wednesday that Congress “must and will” act after Turkey launched an offensive in northern Syria against Kurdish forces previously backed by the United States.

“President Trump’s decision to withdraw U.S. forces from northern Syria is having sickening and predictable consequences,” Cheney said in a statement Wednesday.

{mosads}“This decision aids America’s adversaries, Russia, Iran, and Turkey, and paves the way for a resurgence of ISIS,” Cheney said. “This action imperils American security and that of our allies. Congress must and will act to limit the catastrophic impact of this decision.”

Cheney’s statement follows a tweet earlier Wednesday in which she said it is “impossible to understand why @realDonaldTrump is leaving America’s allies to be slaughtered and enabling the return of ISIS.”

Trump’s decision to withdraw U.S. forces from northern Syria has been met with widespread GOP criticism. Many Republican lawmakers have accused Trump of betraying a U.S. ally. 

In addition to Cheney’s statement Wednesday, typical Trump ally Sen. Lindsey Graham (R-S.C.) said on “Fox & Friends” that Trump’s move could be “be the biggest mistake of his presidency” and said on Twitter the Trump administration has “shamelessly abandoned” the Kurds.

Turkey launched air strikes on the area on Wednesday after Turkish President Recep Tayyip Erdoğan announced over Twitter that the offensive would begin. Erdoğan dubbed the effort by the Turkish military and a Syrian militia as Operation Peace Spring.

Ankara has long threatened to attack Kurdish forces in Syria, but held off while U.S. troops acted as a buffer.

The U.S. military relied on the Syrian Democratic Forces (SDF), which is led by the Kurds, as the local ground force fighting ISIS. Ankara considers the Syrian Kurds terrorists who are an extension of a Kurdish insurgency within Turkey.

Kurdish forces reported Tuesday night that ISIS fighters launched attacks in Raqqa, Syria, in a move seen as the terrorists taking advantage of the chaos to come.

Erdoğan’s office also said Wednesday he spoke by phone with Russian President Vladimir Putin about the incursion.

Cheney mentioned both issues in her comments lacerating Trump’s decision.

“Turkey is invading Syria in reported coordination with Russian-backed forces, ISIS terrorists are launching attacks in Raqqa, and thousands of ISIS fighters are biding their time in makeshift prisons,” Cheney said. “The U.S. is abandoning our ally the Kurds, who fought ISIS on the ground and helped protect the U.S. homeland.”