Washington (CNN)The arms control framework curbing a US-Russian arms race came under further strain this week as Russian President Vladimir Putin took formal steps to withdraw from a landmark nuclear missile treaty and the US charged that Moscow is violating a separate pact that bans all nuclear explosions.

Putin submitted a bill to parliament Thursday to withdraw Russia from the Intermediate-Range Nuclear Forces Treaty, following the Trump administration’s February announcement that it would pull out of the pact because Russia has violated it since 2014, which Moscow denies.

On Wednesday, the US military’s top intelligence officer said the Trump administration believes Moscow is violating a treaty banning all nuclear explosions, a claim that arms control experts questioned and the international body that monitors the treaty could not confirm.

Lt. Gen. Robert Ashley, director of the US Defense Intelligence Agency, told an audience at the Hudson Institute that the US believes Moscow is violating the Comprehensive Nuclear Test Ban Treaty’s “zero yield” standard, which forbids tests strong enough to create a self-sustaining chain reaction that can lead to a nuclear explosion.

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