Joe BIden
Joe BIdenREUTERS/Evelyn Hockstein

US President Joe Biden said on Thursday the world risks nuclear "Armageddon" for the first time since the Cold War.

"We have not faced the prospect of Armageddon since Kennedy and the Cuban missile crisis" in 1962, Biden said at a Democratic Party fundraising event in New York, according to AFP.

He added that Russian President Vladimir Putin is "not joking" when he threatens to use nuclear weapons to pursue his invasion of Ukraine.

Referring to the nuclear standoff 60 years ago triggered by the Soviet Union stationing missiles in Cuba, within easy range of the United States, Biden said that for the "first time since the Cuban missile crisis, we have a direct threat from the use of nuclear weapons if in fact things continue down the path they are going."

"We're trying to figure out what is Putin's off-ramp," Biden said.

"We've got a guy I know fairly well," he continued, before adding, that Putin is "not joking when he talks about potential use of tactical nuclear weapons or biological or chemical weapons, because his military is, you might say, significantly underperforming."

But "I don't think there's any such thing as the ability to easily (use) a tactical nuclear weapon and not end up with Armageddon," Biden said.

"Where does he find a way out?" Biden asked. "Where does he find himself in a position that he does not, not only lose face, but lose significant power within Russia?"

Putin issued a thinly veiled nuclear threat in a recent speech in which Putin also announced his country's first wartime military mobilization since World War Two.

Biden, in his speech at the United Nations General Assembly, then accused Putin of making "overt nuclear threats against Europe" in reckless disregard for nuclear nonproliferation responsibilities.

US National Security Adviser Jake Sullivan said last week that Washington takes Putin's nuclear threats seriously but does not presently see indications of the use of nuclear weapons by Russia.

"There is a risk, given all the loose talk and nuclear saber rattling by Putin, that he would consider this and we’ve been equally clear about what the consequences would be," Sullivan told reporters, but added, "We do not presently see indications about the imminent use of nuclear weapons."

Asked if the US would actively enter the war if Putin used nukes on Ukraine, Sullivan replied, "So, I have said before that we have had the opportunity to communicate directly to Russia a range of consequences...and the kinds of actions the United States would take."