The vast majority of Senate Republicans backed Majority Leader Mitch McConnell on Thursday in a rebuke of President Trump’s rationale for withdrawing U.S. troops from Syria and Afghanistan, voting to declare that the Islamic State’s continued operations in both countries poses a serious threat to the United States.

The measure was presented as an amendment to a greater Middle East policy bill that has yet to pass the Senate and will face challenges in the House, particularly due to a provision regarding Israel-focused boycotts. But the vote is nonetheless an unmistakable sign of Republicans’ growing frustrations with the president, particularly when it comes to some of the decisions he has made as commander in chief.

Last month, the president announced he would be withdrawing American military personnel from Syria, stating in a Twitter post that: “We have defeated ISIS in Syria, my only reason for being there during the Trump presidency.”