"We have no reason to adjust our strategic nuclear posture because we have no indications that Russia is preparing to use nuclear weapons in an imminent manner," a White House spokeswoman said Friday.

This clarification by spokeswoman Karen Jean-Pierre comes after strongly worded statements, Thursday, by President Joe Biden, in which he considered that for the first time since the Cold War the world is facing the threat of an "end of the world" war against the backdrop of the Russian military operation in Ukraine.

In response to a question about whether this high-pitched tone of warning is related to new intelligence obtained by the United States, she replied, "No," during a brief press briefing on the plane carrying Joe Biden to northwest Washington.

Jean-Pierre considered Russia's statements on the use of nuclear weapons "irresponsible", adding that "Biden's statements show how serious it is in dealing with Russia's nuclear threats."

Biden said Thursday in New York, "We haven't faced the prospect of a battle leading to the end of the world since (President John) Kennedy and the Cuban missile crisis in 1962, adding: "We are trying to understand how (Russian President Vladimir) Putin will find a way out."

Russian President Vladimir Putin alluded to the use of a nuclear bomb in a televised speech on September 21, on the impact of field gains made by Ukrainian forces that receive military assistance from Western countries.

Putin expressed his readiness to use "every means" available in his arsenal to confront the West, accusing it of seeking to "destroy Russia."