The so-called New START Treaty was signed by Russia and the U.S. in 2010. It caps the number of long-range nuclear warheads they can deploy and limits the use of missiles that can carry atomic weapons.

Putin said Tuesday in a major address that Russia was not fully withdrawing from the treaty yet.

He said Russia must stand ready to resume nuclear weapons tests if the US does so.

NATO chief Jens Stoltenberg slammed Russia's decision, saying it marked the end of Europe's post-Cold War arms control architecture.

"I regret today's decision by Russia to suspend its participation in the New START treaty," Stoltenberg told a news conference.

"Over the last years Russia has violated and walked away from key arms control agreements. With today's decision on New START the whole arms control architecture has been dismantled."

In his first reaction, US Secretary of State Antony Blinken said Russia arms treaty suspension "deeply unfortunate and irresponsible", but he stressed that the US was willing to talk about the issue.

"We remain ready to talk about strategic arms limitations at any time with Russia, irrespective of anything else going on in the world or in our relationship," Blinken told reporters at the American embassy in Athens during a regional visit.

"We'll be watching carefully to see what Russia actually does. We'll of course make sure that in any event we are postured appropriately for the security of our own country and that of our allies," he added.