Russian President Vladimir Putin declared Tuesday that Moscow was suspending its participation in the New START treaty — the last remaining nuclear arms control pact with the United States — sharply upping the ante amid tensions with Washington over the fighting in Ukraine.

Speaking in his state-of-the-nation address, Putin also said that Russia should stand ready to resume nuclear weapons tests if the U.S. does so, a move that would end a global ban on nuclear weapons tests in place since Cold War times.

Explaining his decision to suspend Russia's obligations under New START, Putin accused the U.S. and its NATO allies of openly declaring the goal of Russia's defeat in Ukraine.

“They want to inflict a ‘strategic defeat’ on us and try to get to our nuclear facilities at the same time," he said.

Putin argued that while the U.S. has pushed for the resumption of inspections of Russian nuclear facilities under the treaty, NATO allies had helped Ukraine mount drone attacks on Russian air bases hosting nuclear-capable strategic bombers.

“The drones used for it were equipped and modernized with NATO's expert assistance,” Putin said. “And now they want to inspect our defense facilities? In the conditions of today's confrontation, it sounds like sheer nonsense.”

Putin emphasized that Russia is suspending its involvement in New START and not entirely withdrawing from the pact yet.

The New START treaty, signed in 2010 by U.S. President Barack Obama and Russian President Dmitry Medvedev, limits each country to no more than 1,550 deployed nuclear warheads and 700 deployed missiles and bombers. The agreement envisages sweeping on-site inspections to verify compliance.

Just days before the treaty was due to expire in February 2021, Russia and the United States agreed to extend it for another five years.

Russia and the U.S. have suspended mutual inspections under New START since the start of the COVID-19 pandemic, but Moscow last fall refused to allow their resumption, raising uncertainty about the pact’s future. Russia also indefinitely postponed a planned round of consultations under the treaty.