WASHINGTON — A senior American general told Congress on Wednesday that Russia has deployed a prohibited cruise missile, the first public confirmation by the United States that the Kremlin had fielded the weapon in violation of a landmark arms control agreement.

The missile is believed to have been moved in December from a test site in southern Russia to an undisclosed operational base.

“We believe that the Russians have deployed a land-based cruise missile that violates the spirit and intent of the Intermediate Nuclear Forces Treaty,” Gen. Paul Selva, the vice chairman of the Joint Chiefs of Staff, told the House Armed Services Committee. “The system itself presents a risk to most of our facilities in Europe,” he added. “And we believe that the Russians have deliberately deployed it in order to pose a threat to NATO and to facilities within the NATO area of responsibility.”

The New York Times reported last month that Russia had deployed a battalion of the prohibited missiles. A typical battalion has four launchers, each of which is equipped with six missiles.