The United States and NATO should prepare for a Russian nuclear strike if a “cornered and delusional” Vladimir Putin should turn to those weapons in his country’s ongoing war in Ukraine, Sen. Mitt Romney says.

Russia’s foreign minister and its ambassador to the U.S. have both signaled that Russia’s “debacle” in Ukraine could lead to a nuclear strike, and Putin himself has noted that he has weapons his opponents do not and that he will “use them, if needed,” according to the Utah Republican.

CIA Director William Burns has warned of the possibility that Putin could use a tactical nuclear weapon, even if there is no “practical evidence” right now to suggest it is imminent.

“We should imagine the unimaginable, specifically how we would respond militarily and economically to such a seismic shift in the global geopolitical terrain,” Romney wrote in an essay for The New York Times over the weekend.

Romney has pointed to Russia as the biggest geopolitical adversary to the U.S. going back to his 2012 presidential campaign, and that it remains a source of great concern for Republicans and Democrats.

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By invading Ukraine, Putin has already proved that he is capable of “illogical and self-defeating” decisions, he said.

The U.S. and NATO would have several options should Putin deploy nuclear weapons, note some would argue for a like response, Romney said.

“NATO could engage in Ukraine, potentially obliterating Russia’s struggling military. Further, we could confront China and every other nation with a choice much like that George W. Bush gave the world after Sept. 11: You are either with us, or you are with Russia — you cannot be with both,” he wrote.

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Romney said he disagrees with those who say that to avoid provoking Russia to stop the prospect of a nuclear strike the U.S. should preemptively restrain Ukraine from routing the Russian military, including limiting weapons, holding back intelligence and pressuring Ukrainian President Volodymyr Zelenskyy to settle.

“The right answer is to continue to give Ukraine all the support it needs to defend itself and to win. Its military successes may force Mr. Putin to exit Ukraine or to agree to a cease-fire acceptable to the Ukrainian people,” he wrote.

Romney voted in favor last week of an $40 billion aid package for Ukraine, including $20 billion for military weapons.

“Failing to continue to support Ukraine would be like paying the cannibal to eat us last,” he said. “If Mr. Putin, or any other nuclear power, can invade and subjugate with near impunity, then Ukraine would be only the first of such conquests.”

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Russia’s use of a nuclear weapon would unarguably be a redefining, reorienting geopolitical event, and a country that chose to retain ties with Russia after such an “outrage” would also become a global pariah, Romney said. The West, he said, represents over half of the global GDP and separating any nation from its combined economies could devastate it.

“The impact on Western economies could be significant, but the impact on the economies of Russia and its fellow travelers would be much worse,” he said. “It could ultimately be economic Armageddon, but that is far preferable to nuclear Armageddon.”

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