During the fundraiser, Biden said that Putin “isn’t kidding when he talks about using tactical nuclear weapons, biological weapons, or chemical weapons.”

NEW YORK — President Joe Biden said Thursday that the risk of nuclear “Armageddon” is at its highest level since the 1962 Cuban Missile Crisis, as Russian officials talk about the possibility of using tactical nuclear weapons after suffering massive setbacks in eight-month invasion of Ukraine.

Speaking at a fundraiser for the Democratic Senate Committee, Biden said Russian President Vladimir Putin was “a guy I know pretty well” and the Russian leader “wasn’t kidding when he talked about using tactical nuclear weapons, biological or chemical weapons.”

Biden added: “We haven’t faced the prospect of Armageddon since Kennedy and the Cuban Missile Crisis.” He suggested that the threat from Putin is real “because his army is – you could say – significantly ineffective.”

US officials have warned for months about the possibility of Russia using weapons of mass destruction in Ukraine as it has faced a series of strategic setbacks on the battlefield, although Biden’s remarks have become the US government’s most stark warnings yet about its nuclear bid.

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It is not yet clear whether Biden had in mind some new assessment of Russia’s intentions. However, as recently as this week, US officials said they do not see any changes in Russia’s nuclear forces that would require a change in the combat readiness posture of US nuclear forces.

“We see no reason to adjust our own strategic nuclear posture, and we have no indication that Russia is preparing to use nuclear weapons imminently,” White House press secretary Karin Jean-Pierre said Tuesday.

The 13-day standoff in 1962, which occurred after the US discovered the Soviet Union’s secret location of nuclear weapons in Cuba, is seen by experts as the closest the world has come to nuclear annihilation. The crisis during the administration of President John F. Kennedy sparked a renewed focus on arms control on both sides of the Iron Curtain.

Biden also challenged Russia’s nuclear doctrine, warning that the use of lower-powered tactical weapons could quickly spiral out of control and lead to global destruction.

“I don’t think there is such a thing as the ability to easily use tactical nuclear weapons and not end up in Armageddon,” Biden said.

He added that he is still “trying to figure out” Putin’s “turn” in Ukraine.

“Where is he looking for a way out?” Biden asked. “Where did he find himself in such a position that he not only lost face, but also significant power in Russia?”

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Putin has repeatedly hinted at the use of his country’s huge nuclear arsenal, including the last month when he announced plans to draft Russian men to serve in Ukraine.

“I want to remind you that our country also has various means of destruction… and if the territorial integrity of our country is threatened in order to protect Russia and our people, we will definitely use all the means at our disposal,” Putin said. Sept. 21, adding, looking into the camera, “It’s not a bluff.”

White House National Security Adviser Jake Sullivan said last week that the US had “clearly” told Russia about the “consequences” of using nuclear weapons in Ukraine.

“This is something that we take very seriously and are in direct communication with Russia, including about the resolute response of the United States should they go down this dark path,” Sullivan said.

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Ukrainian President Volodymyr Zelensky said earlier Thursday that Putin understands that “the world will never forgive” a Russian nuclear strike.

“He understands that after the use of nuclear weapons, he will no longer be able to save, so to speak, his life, and I am sure of that,” Zelensky said.

Biden’s comments came during a private fundraiser for Democratic Senate candidates at the Manhattan home of James and Catherine Murdoch. He tends to be more vulnerable — often speaking only in rough notes — in a setting open only to a handful of reporters without cameras or recording devices.

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