President Donald Trump’s decision to remove U.S. troops from Syria was called a “betrayal” in a joint statement issued by U.S. Sen. Chris Murphy of Connecticut and Utah Sen. Mitt Romney.

“The president’s decision to abandon our Kurdish allies in Northern Syria in the face of an assault by Turkey is a betrayal that will have grave humanitarian and national security consequences,” the statement said. “After enlisting support from the Kurds to help destroy ISIS and assuring Kurdish protection from Turkey, the U.S. has now opened the door to their destruction.”

Earlier Monday, Murphy shared some of the history of the conflict on Twitter: “The U.S. convinced the Kurds to destroy ISIS for us, causing massive Kurd casualties. Then we conned the Kurds into dismantling their defenses, promising to protect them. Now Trump invites the Turks into Syria, green lighting them to wipe out the Kurds.”

In the joint statement, Romney and Murphy said the move to withdraw troops “severely undercuts America’s credibility as a reliable partner and creates a power vacuum in the region that benefits ISIS.”

Romney and Murphy are, respectively, chairman and ranking member of the Senate Foreign Relations Subcommittee on Near East, South Asia, Central Asia, and Counterterrorism.

“This decision is ultimately a victory for Assad, Russia, Iran, and ISIS,” the statement said. “The Administration must immediately reconsider its announced decision to withdraw the few remaining U.S. troops who, for the time being, are playing a vital peacekeeping role.”

Trump, in a Monday tweet, said that Turney should “watch over the captured ISIS fighters and families.”

If they did not, Trump threatened consequences.

“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,” the president said on Twitter.