Defiant Biden throws down gauntlet to Democrats

President Joe Biden insisted again Monday he would not quit the US election race, as the White House denied he had Parkinson's disease following a disastrous debate performance.

The 81-year-old dared Democratic critics to either challenge him at next month's party convention in Chicago or back him against Donald Trump

The president lashed out in both a letter to Congress and a rare call to a television program, at the start of a critical week that includes a NATO summit in Washington where he will face fresh scrutiny.