Russian President Vladimir Putin on Thursday signed a law revoking Russia’s ratification of the Comprehensive Nuclear Test Ban Treaty, a move that was strongly criticized by the United States.

The CTBT is a 1996 treaty that bans all nuclear explosions, including live tests of nuclear weapons.

However, it has never come into force because some key countries, including the United States and China, have never ratified it.

The West has accused Russia of using reckless nuclear rhetoric since it launched its invasion of Ukraine last February.

US Secretary of State Antony Blinken condemned Putin’s announcement on Thursday, calling it a “significant step in the wrong direction.”

“It continues Moscow’s disturbing and misguided effort to heighten nuclear risks and raise tensions as it pursues its illegal war against Ukraine,” Blinken said in a statement.

Putin last week oversaw ballistic missile drills in what Defense Minister Sergei Shoigu said was practice for a “massive” retaliatory nuclear strike against an unnamed enemy.

The Russian strongman also said last month that he was “not ready to say” whether Russia would carry out live nuclear tests.