Democratic U.S. President Joe Biden delivered a shaky performance at a debate on Thursday, while his Republican rival Donald Trump battered him with a series of often false attacks, as the two oldest presidential candidates ever exchanged deeply personal insults ahead of November's election.

The two men traded barbs on abortion, immigration, the wars in Ukraine and Gaza, their handling of the economy — and even their golf games — as they each sought to shake up what opinion polls show has been a virtually tied race for months.

Two White House officials said Biden had a cold. But the president's uneven performance rattled some Democrats and could deepen voter concerns that the 81-year-old is too old to serve another four-year term.