US intelligence agencies have concluded that Russia has deployed a cruise missile in violation of a Cold War-era arms control treaty, a Trump administration official said.
The alleged violation complicates the outlook for US-Russia relations amid turmoil on President Donald Trump's national security team.
The Obama administration three years ago accused the Russians of violating the 1987 Intermediate-Range Nuclear Forces (INF) Treaty by developing and testing the cruise missile.
Officials had anticipated that Moscow would eventually deploy it.
Russia denies it has violated the INF Treaty.
An administration official said intelligence agencies assessed the missile became operational late last year.
The missile deployment was first reported by The New York Times.