WASHINGTON ― Allies and critics of U.S. President Donald Trump on Capitol Hill offered a harsh rebuke to the commander in chief Monday in response to his decision to suddenly withdraw U.S. troops from northeastern Syria, essentially clearing the path for a Turkish military invasion of the region.

“This impulsive decision by the president has undone all the gains we’ve made, thrown the region into further chaos; Iran is licking its chops, and if I’m an ISIS fighter, I’ve got a second lease on life,” Sen. Lindsey Graham, R-S.C., said during an appearance on “Fox & Friends,” using an acronym for the Islamic State group.

"To those who think ISIS has been defeated, you will soon see; and to Turkey, you have destroyed the relationship, what little you had, with the U.S. Congress, and I will do everything I can to sanction Turkey’s military and their economy if they step one foot into Syria.”

Graham tweeted that he will introduce a measure to levy “bipartisan sanctions against Turkey if they invade Syria and will call for their suspension from NATO if they attack Kurdish forces who assisted the U.S. in the destruction of the ISIS Caliphate.” His co-sponsor would be Maryland Democratic Sen. Chris Van Hollen, an advocate of enacting legally mandated sanctions on Turkey since it took possession of the Russian S-400 missile defense system.

The White House late Sunday announced that U.S. forces in northeast Syria will move aside, which Trump followed up Monday with a flurry of tweets, vowing it was time to remove the United States from “ridiculous endless wars” and “bring our soldiers home.” The U.S. had asked European and Middle Eastern countries to take back ISIS fighters captured over the last two years, but Trump said he will turn them all over to Turkey.

“Turkey, Europe, Syria, Iran, Iraq, Russia and the Kurds will now have to … figure the situation out, and what they want to do with the captured ISIS fighters in their ‘neighborhood.’ They all hate ISIS, have been enemies for years. We are 7000 miles away and will crush ISIS again if they come anywhere near us!” Trump tweeted.

Once again @realDonaldTrump uses Rand Paul’s “endless wars” talking points as he orders America to once again abandon our friends and give Russia & Iran exactly what they want. This is wrong. #Syria — Adam Kinzinger (@RepKinzinger) October 7, 2019

But Graham, a staunch Trump ally, called the move “unnerving to its core” because of the potential threat it poses to U.S. national security. He also took to Twitter to blast the move as “shortsighted and irresponsible" and “a disaster in the making,” vowing to introduce measures putting new sanctions on Turkey and forcing the president to reverse the decision, which he predicted would receive strong bipartisan support.

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My late afternoon, Trump’s decision drew criticism from across the political spectrum, to include both House Speaker Nancy Pelosi, D-Calif., and Senate Majority Leader Mitch McConnell, R-Ky.

“I urge the President 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 said in a statement. Pelosi was stronger, saying Trump was again, “deserting an ally in a foolish attempt to appease a foreign strongman.”

Sen. Tim Kaine, D-Va. and a member of the House Armed Services Committee, blasted the move as “a betrayal of a key partner in our fight against ISIS.” He demanded a full briefing to explain the moves to key congressional committees.

“Trump took this step against the advice of our diplomats and military leaders,” Kaine said in a statement. “He didn’t even notify the Kurds, our allies, or Congress. The Trump Doctrine continues — abandon allies and embolden adversaries.”

Sen. Bernie Sanders, I-Vt., previously called for the United States to “responsibly end” military interventions in the Middle East, but he described the sudden shift as “extremely irresponsible” and “likely to result in more suffering and instability.”

The move in the region injects a new plot line into the drama surrounding Trump, who has been focus of a House impeachment inquiry. Defense Secretary Jim Mattis and Syria envoy Brett McGurk resigned from their positions in December over Trump’s call for a complete U.S. withdrawal, which Trump later reversed.

The new policy shift in line with Trump’s original intent comes amid changes at the top of Trump’s national security team in recent weeks ― the departure of national security adviser John Bolton, and the installation of Joint Chief Chairman Gen. Mark Milley and Defense Secretary Mark Esper. Trump also reportedly ordered a substantial reduction in the staff of the National Security Council under new national security adviser Robert O’Brien.

We must always have the backs of our allies, if we expect them to have our back. The Kurds were instrumental in our successful fight against ISIS in Syria. Leaving them to die is a big mistake. #TurkeyIsNotOurFriend — Nikki Haley (@NikkiHaley) October 7, 2019

On Monday, McGurk lambasted the president as “impulsive” and criticized Secretary of State Mike Pompeo for missing in action during the “reckless gamble.” Trump, McGurk said, has “no process to assess facts, develop options, or prepare contingencies. Our personnel are left exposed at the slightest moment of friction.”

“Donald Trump is not a Commander-in-Chief,” McGurk tweeted. “He makes impulsive decisions with no knowledge or deliberation. He sends military personnel into harm’s way with no backing. He blusters and then leaves our allies exposed when adversaries call his bluff or he confronts a hard phone call.”

The White House announcement came after after a phone call between Trump and Turkish President Recep Tayyip Erdogan, who has threatened for months to launch the military operation across the border. He views the Kurdish forces as a threat to his country. Republicans and Democrats have warned that allowing the Turkish attack could lead to a massacre of the Kurds and send a troubling message to American allies across the globe.

On Monday, Syrian Democratic Forces spokesman Mustafa Bali said on Twitter that his forces are determined to defend the area at all costs, while “US forces did not fulfill their responsibilities and began withdrawing from border, leaving the area to turn into a war zone.”

Last month, the SDF announced it had begun withdrawing its fighters from the border towns of Tal Abyad and Ras al-Ayn as part of a deal for the so-called safe zone in northeast Syria involving the U.S. and Turkey. Ankara had wanted American-backed Syrian Kurdish fighters to pull back from the border.

Erdogan, at the time, threatened to launch a unilateral offensive into northeastern Syria if plans to establish the safe zone failed to meet his expectations, including a demand that Turkish soldiers control the corridor.

Strongly disagree with @POTUS Trump decision to allow Erdogan to invade Syria. Betrays Kurds, strengthens ISIS and endangers American homeland. — Rep. Pete King (@RepPeteKing) October 7, 2019

On Twitter, Sen. Marco Rubio, R-Fla., a member of the Senate Foreign Relations Committee, called the U.S. “retreat” a “grave mistake” that would confirm Iran’s view ― likely, Rubio means the view that Trump is averse to using military force ― and embolden the country to “escalate hostile attacks which in turn could trigger much broader & more dangerous regional war.”

The top Democrat on the Senate Intelligence Committee was among lawmakers who said Trump had damaged the faith of allies in the U.S. “The Syrian Kurds stood with the United States in the fight against ISIS, and this President just betrayed them in a tweet,” Sen. Mark Warner, D-Va., said in a tweet. “This will further destabilize the region and haunt the United States for years to come. How can anyone trust the United States under this President?”

Sen. Chris Murphy, D-Conn., a member of the Senate Foreign Relations Committee, likewise said in a post that Trump’s decision would ensure Iran dominates Syria, which will “eventually become a nightmare for Israel."

“Yes, Trump doublecrossed the Kurds, but really a total lack of foreign policy imagination created this crisis,” Murphy said. “Trump wasted the last 30 months. Could have flooded northern Syria w political/diplomatic resources to find a governance structure that both Kurds/Turks could accept.”