"This is the last existential threat. It is climate. We have a crazy SOB like that guy Putin and others and we always have to worry about nuclear conflict, but the existential threat to humanity is climate," Biden told a small group of donors.

Biden has previously cursed "son of a bitch" at others. In January 2022, he was caught on the hot mic using the same term of abuse against a Fox News White House reporter.

(Reporting by Trevor Hunnicutt and Nandita Bose in Washington; Editing by Sonali Paul)