WASHINGTON — Both Democratic and Republican lawmakers reacted with disbelief over President Donald Trump’s sudden decision this week to withdraw all U.S. military forces from Syria, expressing concern that the move could be a dangerous strategic mistake.

Just hours after the president released a video stating that “we have won against ISIS,” a bipartisan group of Senate Armed Services Committee members released a letter pleading with him to reconsider his stance.

“Such action at this time is a premature and costly mistake that not only threatens the safety and security of the United States but also emboldens ISIS, (Syrian leader) Bashar al Assad, Iran and Russia,” the letter said.

“If you decide to follow through with your decision to pull our troops out of Syria, any remnants of ISIS in Syria will surely renew and embolden their efforts in the region.”

The group was led by Sen. Lindsey Graham, R-S.C., and a staunch defender of Trump in recent months. However, on this move, he blasted Trump, leveling the same criticisms he used against former President Barack Obama when he withdrew U.S. forces from Iraq after that war.

“I fear it will lead to devastating consequences for our nation, the region, and throughout the world,” he said on social media.

Senate Armed Services Committee ranking member Jack Reed, D-R.I., called the “hasty, disjoined” withdrawal announcement “further evidence of President Trump’s inability to lead on the world stage.” He criticized the president for ignoring assessments from his own staff in making the decision.

“Just because President Trump tweets that he has defeated ISIS doesn’t make us safer, especially when the reality is very different on the ground,” he said. “The president continues to disregard the advice of his military, diplomatic, and intelligence personnel who have consistently warned against the action the president seems poised to take.”

Senior administration officials have downplayed the suddenness of the move, arguing that Trump’s antipathy towards U.S. military involvement in Syria has been well known since his presidential campaign.

But both military and State Department leaders — many of whom in recent days had downplayed the chances of a full withdrawal of forces from the region — appeared caught off guard by the commander in chief’s decision, adding to the frustration on Capitol Hill.

Rep. Adam Schiff, D-Calif., and the incoming chairman of the House Intelligence Committee, said he was “deeply concerned that the President is making yet another abrupt decision, with seemingly little input or consultation with military and intelligence officials.” He promised a full review of the move.

Sen. Ben Sasse, R-Neb., went even further in his criticism.

"Eight days ago the administration called a hypothetical pullout ‘reckless.’ Today, we're leaving,” he said.

“The president's generals have no idea where this weak decision came from: They believe the high-fiving winners today are Iran, ISIS and Hezbollah. The losers are Israel, humanitarian victims and U.S. intelligence gathering. A lot of American allies will be slaughtered if this retreat is implemented.”

White House and Pentagon officials have not confirmed a timeline for withdrawal, although multiple media sources have quoted defense officials as saying they have been instructed to move quickly on bringing troops home.

One lawmaker who offered faint praise for the move was Rep. Barbara Lee, D-Calif., and an outspoken opponent of multiple U.S. overseas combat operations. She signaled support for the move helping to “bring these endless wars to a close” but also criticized how the withdrawal is being handled.

“As we draw down our military role in Syria, the U.S. must redouble our diplomatic negotiations to broker peace in the region,” she said. “President Trump should not be celebrating walking away from a humanitarian crisis, especially one that the United States helped create.”