Biden made this known during a fundraiser on Thursday amid the threat Russian President Vladimir Putin will deploy nuclear weapons to ward off Ukraine’s attempt to reclaim control of Moscow-occupied areas.
United States President, Joe Biden has said that the risk of nuclear "Armageddon" is at the highest level since the 1962 Cuban Missile Crisis.
Biden made this known during a fundraiser on Thursday amid the threat Russian President Vladimir Putin will deploy nuclear weapons to ward off Ukraine’s attempt to reclaim control of Moscow-occupied areas.
According to Al Jazeera, Biden's warning is said to follow talks among Russian officials about the possibility of using tactical nuclear weapons after suffering massive setbacks in the eight-month invasion of Ukraine. Russian President Putin has also repeatedly alluded to using his country's vast nuclear arsenal.
"We have not faced the prospect of Armageddon since Kennedy and the Cuban Missile Crisis," Biden said at a fundraiser for the Democratic Senatorial Campaign Committee, suggesting Putin's threat is real "because his military is you might say significantly underperforming."
The US and the EU have previously said Mr Putin's nuclear sabre-rattling should be taken seriously.
However, the US National Security Adviser Jake Sullivan last week said that despite Moscow's nuclear hints, the US had seen no signs that Russia was imminently preparing to use a nuclear weapon.
"For the first time since the Cuban Missile Crisis, we have a direct threat to the use of nuclear weapons, if in fact, things continue down the path they'd been going," Mr Biden told fellow Democrats.
"We have not faced the prospect of Armageddon since Kennedy and the Cuban Missile Crisis."
In 1962, the US and the Soviet Union - under President John F Kennedy and Nikita Khrushchev - came close to a nuclear showdown over the deployment of Russian nuclear weapons in Cuba.
The confrontation is considered by many experts to be the closest the world has ever come to full-scale nuclear war.
During a speech last Friday, President Putin said the US had created a "precedent" by using nuclear weapons against Japan at the end of World War Two, a comment that would not have gone unnoticed by Western governments, BBCNews Russia editor Steve Rosenberg pointed out.
Mr Putin has also threatened to use every means at his disposal to protect Russian territory.
For months, U.S. officials have warned of the possibility of Russia using weapons of mass destruction in Ukraine. But officials said this week that they have seen no change to Russia's nuclear forces that would require a change in the alert posture of U.S. nuclear forces.
The U.S. has been "clear" to Russia about what the "consequences" of using a nuclear weapon in Ukraine would be, according to White House national security adviser Jake Sullivan.