U.S. Sen. Lamar Alexander said Monday that he will vote against military action in Syria.

“America’s credibility is not helped” by this kind of military strike, Alexander told reporters shortly before a speech to the Rotary Club of Nashville. The statement marks the first time that Alexander has said definitively that he will vote against a resolution authorizing a strike on Syria.

“I will vote ‘no’ because I see too much uncertainty about what comes next,” Alexander said.