Turkey launched its military operation to flush Kurds allied with the US out of northeastern Syria Wednesday, sparking outrage in Congress and creating rare bipartisan unity about the risks to Kurds, US national security interests, regional stability and the fight against ISIS.

The attack has highlighted a rare Republican willingness to directly criticize President Donald Trump, who apparently gave Turkish President Recep Tayyip Erdogan the go-ahead on Sunday to proceed with his long-planned move against Kurdish fighters who make up part of the Syrian Defense Forces who had fought against ISIS with the US.

The White House announced that US troops would move out the way and would not support or be involved in the operation.

"News from Syria is sickening," Rep. Liz Cheney of Wyoming, the third-ranking Republican in the House, tweeted Wednesday, echoing lawmakers across the spectrum. "Turkish troops preparing to invade Syria from the north, Russian-backed forces from the south, ISIS fighters attacking Raqqa. Impossible to understand why @realDonaldTrump is leaving America's allies to be slaughtered and enabling the return of ISIS."

'Millions have died'

Both Pentagon and State Department officials had advised Trump against making the move, arguing a US presence is needed to counter ISIS and keep Iran and Russia, both influential inside Syria, in check.

Democratic Rep. Ro Khanna of California raised a question many analysts and lawmakers were airing: Why would Trump not push for some concession or arrangement with the Turkish leader, and instead seem to offer him carte blanche against allies who died fighting for a US cause?

"We have extraordinary leverage with Erdogan: why wouldn't the President get a deal with Turkey before withdrawing US troops?" Khanna said. "This war will destabilize the region, and possibly allow ISIS to regain power in the area."

The wave of criticism -- including from a usually acquiescent Republican Party and in particular from some staunch Trump allies -- seemed to have stung the President and pushed him into damage control mode. On Wednesday afternoon, he released a statement that did not mention his role in giving Erdogan the green light or the fate of the Kurdish fighters.

'A bad idea'

"This morning, Turkey, a NATO member, invaded Syria. The United States does not endorse this attack and has made it clear to Turkey that this operation is a bad idea. There are no American soldiers in the area," Trump said. "From the first day I entered the political arena, I made it clear that I did not want to fight these endless, senseless wars—especially those that don't benefit the United States."

Trump said Turkey had "committed to protecting civilians, protecting religious minorities" and "ensuring no humanitarian crisis takes place," and said Ankara "is now responsible for ensuring all ISIS fighters being held captive remain in prison and that ISIS does not reconstitute in any way, shape, or form."

Earlier Wednesday, Trump had taken angrily to Twitter, also to push back on criticism.

"The United States has spent EIGHT TRILLION DOLLARS fighting and policing in the Middle East," he tweeted. "Thousands of our Great Soldiers have died or been badly wounded. Millions of people have died on their side. GOING INTO THE MIDDLE EAST IS THE WORST DECISION EVER MADE... IN THE HISTORY OF OUR COUNTRY"

The President appeared to reference the 2003 invasion of Iraq, which was premised on faulty and manipulated intelligence that former leader Saddam Hussein had weapons of mass destruction. "There were NONE!" Trump tweeted. "Now we are slowly & carefully bringing our great soldiers & military home. Our focus is on the BIG PICTURE!"

But analysts and lawmakers of all stripes are arguing that the big picture and the benefits to the US of standing its ground are exactly what Trump is missing, pointing to ramifications for future US alliances and the fight against ISIS, which remains a threat, among other issues. Many also argue that the withdrawal announcements seem anything but slow and careful.

Texas Republican Rep. Will Hurd was among the lawmakers announcing support for legislation by fellow Republican Sen. Lindsey Graham of South Carolina and Democratic Sen. Chris Van Hollen of Maryland to sanction Turkey's economy and military for the Syria operation.

'Sanctions from hell'

"Just as the Kurds had our backs against ISIS, we must have theirs," Hurd said. "The U.S. must do whatever it takes to hold Turkey accountable for compromising our security."

Graham had warned Turkey on Tuesday of "sanctions from hell," if it moved forward with the attack.

The South Carolina Republican, usually a stalwart Trump ally, is predicting the legislation will have a veto-proof majority in the Senate, making it impossible for Trump to stop. He has been publicly scathing in his criticism of the President for the Turkey decision.

On Wednesday, Graham called the situation "a disaster in the making" in a series of tweets and urged Trump "to change course while there is still time."

As if to confirm lawmakers' concerns, the Syrian Democratic Forces said in a statement Wednesday that they were suspending military operations against ISIS in northern Syria following the "Turkish aggression."

The International Rescue Committee expressed deep concern about impact on "the lives and livelihoods of the two million civilians in northeast Syria who have already survived ISIS brutality and multiple displacements."

IRC said the military offensive "could displace 300,000 people and disrupt life-saving humanitarian services," including its own.