Republicans and Democrats on the House Armed Services Committee say they are launching an unusual bipartisan campaign to push back against President Donald Trump’s proposed withdrawal of all U.S. forces from Syria.

Texas Republican Mac Thornberry, the committee’s chairman, and Washington Democrat Adam Smith, the ranking member and likely the new chairman in the next Congress, said in separate interviews Thursday that they will join forces to try to slow or shape, if not stop, the president’s move. It was their first public comments on the issue.

Similar bipartisan alarms have rung in the Senate Armed Services Committee.

The House Armed Services campaign may begin with a rare joint statement by Thornberry and Smith, which they expect to release later Thursday. It may also include efforts to support the president’s top advisers as they attempt to set the terms on how the withdrawal plays out, the senior lawmakers said.

In the interviews, Thornberry and Smith previewed their statement and expressed unequivocal criticism of the president’s move.

Thornberry’s criticism of the president is noteworthy because the two men are ordinarily in agreement on numerous policies, including on military strategy and especially on defense spending.

Thornberry said the administration did not consult him on the decision, though the chairman said he was notified of it shortly before the president suggested in a Wednesday morning tweet that an announcement on pulling all 2,000 or so U.S. troops from Syria was nigh.

“We have defeated ISIS in Syria, my only reason for being there during the Trump Presidency,” the president tweeted, in a reference to the Islamic State militant group.

Asked about the president’s decision on Thursday, Thornberry said: “I think it was a mistake.”

“My opinion is that we have a number of important interests — including terrorism and Iran and reliability with allies, and all those interests are damaged significantly if the U.S. completely withdraws,” Thornberry said. “We’ve seen what happens when the U.S. abruptly withdraws from some place. And it’s not good.”

Smith agreed and indicated that overseeing the planned pullout from Syria will not only be a priority of House Armed Services under his leadership, starting in January, but is already a matter of intense discussions on the committee.

“We’re going to look into it as soon as possible, because I think it is the exact wrong decision,” Smith said. “ISIS is not defeated. As has been pointed out, I think just in the last week we’ve had over 200 raids against ISIS targets in Syria. So, snatching defeat from the jaws of victory is one big problem.”

The other big problem, Smith said, concerns America’s Kurdish allies, who have borne the brunt of the fighting against ISIS in Syria as well as in Iraq.

“We would not have been successful against ISIS in either Iraq or Syria if it was not for the Kurds,” Smith said. “And now we are abandoning them as Turkey threatens them. The only thing holding the Turks off, to the extent they have been held off, is our presence.”

Thornberry and Smith indicated they are looking to influence decision makers in the Trump administration on the issue.

“I don’t know a single serious national security person, Democrat or Republican, who agrees with the decision he has made,” Smith said. “So, in a bipartisan way, we’re going to push back on it and try to get the president to change his mind. Mr. Thornberry and I are talking and trying to figure out how we should approach it.”

Thornberry, for his part, also suggested that lawmakers who oppose the withdrawal would try to reshape the president’s move.

“Obviously, the No. 1 consideration has to be the security of our forces, whatever decisions are made,” Thornberry said. “No. 2: Is there some other middle path that protects our interests but moves toward what the president seems to want to do? I don’t know.”

On the other side of the Capitol, senators on both sides of the aisle have also criticized the move. Six senators wrote Trump on Wednesday to urge him to reconsider his Syria plan.

“We believe that 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, Bashar al Assad, Iran, and Russia,” the senators wrote.

The signatories were four Republicans — Lindsey Graham of South Carolina, Marco Rubio of Florida, Tom Cotton of Arkansas and Joni Ernst of Iowa — plus Democrat Jeanne Shaheen of New Hampshire and Angus King, an independent from Maine who caucuses with Democrats.

All but Rubio are on Armed Services, and Rubio serves on Foreign Relations.

Jack Reed of Rhode Island, the top Democrat on Senate Armed Services, has also criticized the withdrawal plan. James M. Inhofe, R-Okla., the Senate committee’s chairman, has expressed concerns and has sought more information but has not yet passed public judgment on the issue.