A top U.S. arms control official on Monday sharply criticized Russia for suspending its participation in the last remaining nuclear weapons treaty, but said Washington will try to work with Moscow to continue its implementation.

Russian President Vladimir Putin announced last week that the country would suspend participation in the New START treaty which obligated both Russia and the U.S. to commit to regular communications on the status of their nuclear arsenals, allow regular on-site inspections and abide by caps on the number of deployed and non-deployed warheads of each side.

"Russia is once again showing the world that it is not a responsible nuclear power," Bonnie Jenkins, the U.S. undersecretary of state for arms control, said at a session of the Conference on Disarmament, a United Nations-affiliated international forum.

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Russia is not withdrawing from the treaty, which is in force until 2026, but Putin said Russia cannot accept U.S. inspections of its nuclear sites while Washington and its NATO allies seek Russia’s defeat in Ukraine. The Russian Foreign Ministry said the country would respect the treaty’s caps on nuclear weapons and continue notifying the U.S. about test launches of ballistic missiles.

The inspections have been dormant since 2020 because of the COVID-19 pandemic. Discussions on resuming them were supposed to have taken place last November, but Russia abruptly called them off.

Jenkins later told reporters that the U.S. has not fully assessed the consequences of Russia's suspension move, but said "we're not seeing any evidence that Russia is in noncompliance."

"We remain ready to work assertively with Russia to fully implement the New START treaty, continued implementation of the treaty based on the best interests of both parties," she said.

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Putin's announcement of suspending participation came just before the first anniversary of Russia sending troops into Ukraine. Putin has repeatedly cast the conflict as necessary to combat alleged Western aims to weaken Russia and has warned of an increasing threat of nuclear war.

Former Russian president Dmitry Medvedev, now deputy head of the national security council, said last week that "If the U.S. wants Russia’s defeat, we have the right to defend ourselves with any weapons, including nuclear."

"Russia must end this war and must cease its irresponsible nuclear rhetoric," Jenkins said.

French Foreign Minister Catherine Colonna also harshly criticized Russia's New START suspension at the Geneva conference as "added proof — if any was needed — of the dangerous impasse that Russia is sealing itself into."