Joe Biden said that the world is facing its biggest threat of a nuclear "Armageddon" since the Cuban missile crisis due to the danger of Vladimir Putin using the weapons over Ukraine.
The US President has said that Washington is still "trying to figure out" where Putin can find a way out from the crisis.
The White House has said repeatedly that it has seen no indication that Russia is preparing to use nuclear weapons despite what it calls Putin's "nuclear sabre-rattling."
