WASHINGTON — 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 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 withdraw American military personnel from Syria, saying in a Twitter post that: “We have defeated ISIS in Syria, my only reason for being there during the Trump presidency.”

The backlash from Republicans was immediate and has remained consistent, as even some of the president’s closest allies have warned him against the dangers of withdrawing from battlefields where the United States has made gains, but by no means has expunged al-Qaida, ISIS and their affiliates.

While the amendment recognizes the work that has been done to push back such terror organizations, it specifically names al-Qaida and ISIS as “a global threat, which merits increased international contributions to the counterterrorism, diplomatic and stabilization efforts underway in Syria and Afghanistan.”

It also notes that “withdrawal of the United States forces from the ongoing fight against these groups … could allow terrorists to regroup, destabilize critical regions, and create vacuums that could be filled by Iran or Russia, to the detriment of United States interests and those of our allies.”

Several Republican senators have warned that Kurdish fighters who have operated in Syria would be left particularly vulnerable if the United States withdraws from the area.

While the Senate’s Thursday vote does not carry the weight of law or prevent the president from pursuing his plans, it puts congressional Republicans on the record as being at odds with Trump’s Middle East policy.

In the past, the Senate has backed similar bipartisan measures expressing support for NATO in the face of Trump’s criticisms and threats to withdraw from the alliance.

Earlier this month, the House overwhelmingly passed a measure to prevent Trump from using any federal funds to execute a withdrawal from NATO.

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