On Thursday, Russian President Vladimir Putin signed a law revoking Russia's ratification of the Comprehensive Nuclear-Test-Ban Treaty, according to a decree published on the government's website.
The 1996 treaty bans all nuclear explosions, including live nuclear weapons tests, although it never entered into force because some key countries – including the US and China – never ratified it.
Russia says the aim is to restore parity with the US, which has signed but not ratified the agreement, and that it will not resume testing unless Washington does so.
The West has accused Russia of using nuclear rhetoric since it launched an offensive against Ukraine last February.
Putin oversaw ballistic missile exercises last Sunday in what Defense Minister Sergei Shoigu said was a drill for a "massive" retaliatory nuclear strike against an unnamed enemy.
The Russian president also said last month that he was "not ready to say" whether Russia would conduct live nuclear tests.
The draft law on revoking the agreement was passed in the Russian parliament last month under an accelerated procedure.
During the parliamentary debate, State Duma Speaker Vyacheslav Volodin said the move to revoke the agreement was a response to US "cynicism" regarding nuclear weapons.
Although it never entered into force, the treaty was ratified by 178 countries, including nuclear powers France and Britain, and has symbolic significance.
Its supporters say it established an international norm against live nuclear weapons testing, but critics say the deal's potential cannot be fulfilled without ratification by major nuclear powers.
The Russian parliament ratified the agreement in June 2000, six months after Putin first became president.
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