Russia Ukraine news: Biden warns of Russia's nuclear threat, says Putin 'not joking' about using weapons of mass destruction

Russia Ukraine news: President Joe Biden said Thursday that the risk of nuclear "Armageddon" is at the highest level since the 1962 Cuban Missile Crisis, as Russian officials speak of the possibility of using tactical nuclear weapons after suffering massive setbacks in the eight-month invasion of Ukraine.

Speaking at a fundraiser for the Democratic Senatorial Campaign Committee, Biden said Russian President Vladimir Putin was "not joking when he talks about the use of tactical nuclear weapons or biological or chemical weapons."

Biden added, "We have not faced the prospect of Armageddon since Kennedy and the Cuban Missile Crisis."

Biden also challenged Russian nuclear doctrine, warning that the use of a lower-yield tactical weapon could quickly spiral out of control into global destruction.

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

US officials for months have warned of the prospect that Russia could use weapons of mass destruction in Ukraine as it has faced a series of strategic setbacks on the battlefield as recently as this week. 

Though, they have said they have seen no change to Russia's nuclear forces that would require a change in the alert posture of US nuclear forces.