Ukrainian President Volodymyr Zelenskyy urged world leaders to act and stop Russian President Vladimir Putin as he warns that Moscow has begun preparations for the possible use of nuclear weapons

"They begin to prepare their society," Zelenskyy said during a BBC interview at the presidential palace in Kyiv. "That's very dangerous. They are not ready to do it, to use it, but they begin to communicate."

"They don't know whether they'll use or not use it," he stressed. "I think it's dangerous to even speak about it."

President Biden on Friday set social media into a frenzy when he said that Putin was "not joking when he talks about the use of tactical nuclear weapons," adding that "we have not faced the prospect of Armageddon since Kennedy and the Cuban Missile Crisis." 

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The White House defended Biden’s comments, saying, "That kind of irresponsible rhetoric we have seen is no way for the leader of a nuclear-armed state to speak, and that’s what the president was making very clear."

A photo of Volodymyr Zelenskyy

Ukrainian President Volodymyr Zelenskyy is seen during his joint press conference with Polish Prime Minister Mateusz Morawiecki and Latvian President Egils Levits in Kyiv, Ukraine, on Sept. 9, 2022. (Alexey Furman/Getty Images)

White House press secretary Karine Jean-Pierre told reporters aboard Air Force One that officials "have not seen any reason to adjust our own strategic nuclear posture." 

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"Nor do we have indications that Russia is preparing to imminently use nuclear weapons," she added. 

Putin

Russian President Vladimir Putin, center, attends the Victory Day military parade marking the 77th anniversary of the end of World War II in Moscow on May 9, 2022. (Mikhail Metzel, Sputnik, Kremlin Pool Photo via AP)

Putin’s rhetoric and policy have grown more aggressive after Ukraine made significant gains and drove back the Russian military in the Donbas region, advancing 25 miles in one day this week after Putin claimed to have annexed the rebel region as part of Russia. 

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Putin last month approved the partial mobilization of Russia’s military, allowing him to call a draft, which sent Russian men fleeing from the country to avoid military service in what has turned into an extremely difficult campaign for Moscow. 

A vehicle on fire after shelling in Donetsk

A vehicle on fire after shelling in Donetsk, an area controlled by Russian-backed separatist forces, in eastern Ukraine on Sept. 17, 2022. (AP Photo/Alexei Alexandrov)

And that has pushed Putin into a corner from which critics fear he will take the most drastic actions. He made renewed threats of using "any force necessary," including nuclear weapons, to defend what he viewed as Russian territory from other nations. 

Rebekah Koffler, a former Defense Intelligence Agency officer and the author of "Putin’s Playbook: Russia’s Secret Plan to Defeat America," told Fox News Digital that Zelenskyy is worried and has reason to be as Putin’s threat to use a nuclear weapon remains a "real possibility" that Western leaders may unintentionally provoke with their rhetoric. 

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"[Zelenskyy] wants the U.S. and NATO to preemptively strike Russia to prevent Putin from unleashing Armageddon on Ukraine, but unintentionally, Zelenskyy as well as Biden … are ratcheting up escalation," Koffler said, explaining that what they see as a deterrent only "feeds into his paranoia."

"Putin views it as his last and decisive battle that he cannot possibly lose because the stakes are of existential nature for Russia and for Putin," she added.