Russian President Vladimir Putin's continued sabre-rattling about detonating a nuclear weapon in his war on Ukraine is a danger not felt worldwide since the 1962 Cuban Missile Crisis, Geraldo Rivera said on "Piers Morgan Uncensored."

In an interview with Fox Nation host Piers Morgan, Rivera said the mutually-assured-destruction dynamic that prevents such dangers is at risk with an "insane" autocrat like the former KGB agent at the top of the Kremlin.

"How it ends, I have no idea, but the nuclear sabre-rattling has rattled me as a child of the 1950s who used to duck under our desks at school in nuclear drills that would have been fruitless," he said.

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Morgan, Rivera (FoxNation)

Morgan, Rivera (FoxNation)

"[A man] who lived through as a cadet in Maritime College, the 1962 Cuban Missile Crisis, this is the worst it's been since then. People have to understand when people are talking about nuclear or use of nuclear weapons in a way that it is plausible, if remote, it is unnerving to me."

Rivera further reported on rumblings that Putin may fire a "tactical" nuke that would detonate over an unpopulated area like the middle of the Black Sea as a "demonstration", calling it further example of his insanity.

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The "Five" host went on to hearken back to grade school and was reminded of something a civics teacher told him that shook him at the time.

Russian President Vladimir Putin attends a meeting of the Supreme Eurasian Economic Council in Yerevan, Armenia.

Vladimir Putin in Yerevan, Armenia. (Shutterstock)

Rivera said the teacher once told him thar Adolf Hitler – if given the choice between suicide or taking an action to end the world – he would have chosen the latter.

Rivera said he fears the same may be true for Putin, who he said appears to be losing in Ukraine after abandoning his quest for Kyiv and instead fighting mercilessly in the Donbas and coastal regions.

"Is Putin now playing with the button because he may lose this ridiculous, stupid war?" he asked.

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Rivera praised the Ukrainian government for its handling of the invasion, and also criticized former President Donald Trump for what he saw as actions seeking to undermine NATO, citing in one case the then-president's concern over nations not paying their 2% commitment.

"He was so disparaging of them, and it sounded like he wanted the Atlantic Alliance gone -- that he didn't even think the United States should be in the in NATO. What if there was no NAITO now?" he asked.

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