WASHINGTON

The US has not detected any indication that Russia is poised to use any of the doomsday weapons in its nuclear arsenal, the White House said on Friday.

Spokeswoman Karine Jean-Pierre continued to assail Russian President Vladimir Putin's "irresponsible" nuclear saber rattling, further maintaining "there's no way to use" nuclear weapons "without unintended consequences."

"It cannot happen. We won't be intimidated by Putin's rhetoric," she told reporters aboard Air Force One. "We have not seen any reason to adjust our own nuclear posture, nor do we have indications they are prepared to use them but Putin can de-escalate this at any time, and there's no reason to escalate."

The comments come one day after US President Joe Biden warned that the world is on the precipice of a nuclear catastrophe for the first time since the Cold War.

“We have not faced the prospect of Armageddon since (President John F.) Kennedy and the Cuban missile crisis,” the president said at a Democratic fundraiser, referring to the 1962 confrontation between the US and Soviet Union that nearly devolved into nuclear warfare.

“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,” he added.

Putin raised the specter of nuclear confrontation last month as he prepared to annex more Ukrainian territory. Putin and his proxies ultimately completed the annexation process this week following referendums denounced by the West as a fraudulent “land grab.”

Biden said he knows Putin “fairly well,” adding he is “not joking when he talks about the potential use of tactical nuclear weapons or biological or chemical weapons, because his military is, you might say, significantly underperforming.”

Ukrainian forces have been making strident advances in territories formerly occupied by Russia, routing them in the northern Kharkiv region and pressing towards a major advance on Kherson in the south.