Russian dictator Vladimir Putin signed a law officially suspending Russia's participation in the New START treaty on Feb. 28.
He first announced the suspension during his state-of-the-nation address to the Federal Assembly and members of the Russian political elite on Feb. 21.
In 2010, the U.S. and Russia signed a treaty in Prague that aimed to reduce their nuclear arms. The pact limits each country to no more than 1,550 deployed nuclear warheads and 700 deployed missiles and bombers. It was the sole agreement governing arms control between the two nations.
During his address, Putin also said that Russia would "not allow" the U.S. or NATO countries to inspect its nuclear arsenal, adding that a week prior, he signed a decree putting new strategic ground-based systems of nuclear missiles on combat duty. He also said that Russia is prepared to test nuclear weapons if the U.S. does so first.
The statement is recent in a series of nuclear threats that Russia has made since the beginning of its full-scale invasion of Ukraine.
Putin's initial announcement was met with fierce criticism from Ukraine's Western allies.
"With today’s decision on New START, the whole arms control architecture has been dismantled," NATO Secretary General Jens Stoltenberg said during a press conference later that day. "I strongly encourage Russia to reconsider its decision and to respect existing agreements."
Responding to Putin's announcement, U.S. National Security Advisor Jake Sullivan said that "nobody is attacking Russia. There’s a kind of absurdity in the notion that Russia was under some form of military threat from Ukraine or anyone else."
