"He's not joking when he talks about the use of tactical nuclear weapons or biological or chemical weapons because his military is you might say significantly underperforming," Mr Biden said of his Russian counterpart. News reporter @samuelosborne93 US President Joe Biden has said the world is facing the biggest threat of nuclear "Armageddon" since the days of President Kennedy and the Cuban Missile Crisis. Speaking at a Democratic Party fundraiser in New York, his 'off camera' comments were overheard by journalists from the White House pool. It comes as Russian officials warned of the possibility of using tactical nuclear weapons after suffering huge military setbacks in the invasion of Ukraine. Moscow accuses Zelenskyy of calling for world war - latest updates Describing Russian President Vladimir Putin, President Biden said he had "got to know the guy pretty well". "He's not joking when he talks about the use of tactical nuclear weapons or biological or chemical weapons because his