On Tuesday, Russian President Vladimir Putin announced that Moscow would suspend its participation in the New START treaty, the last nuclear arms control treaty with the US, sharply upping the ante amid tensions with Washington over the war in Ukraine.

In his State of the Union address, Putin also said Russia should stand ready to resume nuclear weapons testing if the US did so, a move that would end a global ban on nuclear weapons testing that dates back to the Cold War.

Explaining his decision to suspend Russia’s obligations under the New START treaty, Putin accused the US and its NATO allies of publicly declaring Russia’s goal of defeating Ukraine.

“They want to inflict a ‘strategic failure’ on us and try to gain access to our nuclear facilities simultaneously,” he said, announcing his decision to suspend Russia’s accession to the treaty. “In this context, I must announce today that Russia will suspend its participation in the Strategic Offensive Arms Treaty.”

The official title of New START is the treaty between the USA and the Russian Federation on Measures for the Further Reduction and Limitation of Strategic Offensive Arms.

US Secretary of State Anthony Blinken condemned Putin’s move as “very unfortunate and irresponsible,” noting that “we will be watching Russia’s actual actions closely.”

He said: “Of course, we will ensure that in any case, for the security of our own country and our allies, we are in the appropriate posture.” Nonetheless, he stressed, “We stand ready to discuss with Russia the issue of limiting strategic arms, no matter what else is going on in the world or our relationship.”

NATO Secretary-General Jens Stoltenberg also regretted Putin’s move, saying, “with today’s decision on New START, the comprehensive arms control architecture has been dismantled.”

Putin has argued that while the US has pushed to resume inspections of Russian nuclear facilities under the treaty, the NATO allies have helped Ukraine launch drone strikes on Russian air bases that host nuclear-capable strategic bombers.

The Russian military said it shot down a Soviet-made drone that struck two bomber bases inside Russia in December. Still, it acknowledged that several service members were killed by debris that also damaged some aircraft.

Putin on Tuesday mocked NATO’s statement urging Russia to allow the US to resume inspections of Russia’s nuclear weapons base, calling it “some kind of absurd drama”.

The Russian leader also pointed out that NATO’s declaration on New START raised the issue of British and French nuclear weapons, which are part of the alliance’s nuclear capabilities but not included in the US-Russian treaty.

Putin stressed that Russia has suspended its participation in New START and has not fully withdrawn from the agreement.

The New START treaty, signed in 2010 by former US President Barack Obama and former Russian President Dmitry Medvedev, limits each country to deploying more than 1,550 nuclear warheads and 700 missiles and bombers. The agreement envisages comprehensive on-site inspections to verify compliance.

Just days before the treaty expired in February 2021, Russia and the US agreed to extend it for another five years.

Russia and the US suspended joint inspections under New START since the start of the COVID-19 pandemic, but Moscow refused to resume them last fall, adding to uncertainty about the future of the agreement. Russia has also postponed indefinitely a round of consultations planned under the treaty.

The US State Department said Russia’s refusal to allow inspections “prevent the US from exercising important rights under the treaty and threatens the viability of US-Russian nuclear arms control.” It noted that nothing prevents Russian inspectors from inspecting US facilities.

Putin on Tuesday disputed US claims that Washington had denied some requests by Russia to visit specific US facilities.

“Under the treaty, we are not allowed to conduct full inspections,” he said. “We can’t really check anything on their side.”

He claimed that the US was working on nuclear weapons and that some in the US were considering plans to resume nuclear testing banned by the global test ban that came into effect after the end of the Cold War.

“In this case, Rosatom (the Russian state nuclear company) and the Ministry of Defence must ensure that Russia’s nuclear weapons tests are ready,” Putin said. “Of course, we won’t be the first to do it, but if the US tests it, we will. No one should have the dangerous illusion that the global strategic balance of power could be disrupted.”