The reported use of the Army Tactical Missile System, known as ATACMS, came as Russian President Vladimir Putin formally lowered the threshold for using nuclear weapons, opening the door to a potential nuclear response by Moscow to even a conventional attack by any nation supported by a nuclear power. That could include Ukrainian attacks backed by the U.S.

A Telegram channel affiliated with the Ukrainian military posted a video Tuesday that it says shows a U.S.-supplied ATACMS missile being fired from an undisclosed location in Ukraine. The Associated Press could not independently verify the date and location the video was filmed.