Joe Biden turns 81 as worries about his age weigh on re-election prospects

US President Joe Biden turns 81 on Monday, a milestone likely to draw attention to his status as the oldest person to ever occupy the Oval Office, with opinion polls showing Americans worried he is too old for the post he is seeking reelection to.

Biden has addressed those who worry that he is too old for the rigors of the White House with humor and an attempt to convince voters that his age and experience over a half-century in public life is an asset in tackling America's problems.

"I know I'm 198 years old," Biden joked back in June.

If re-elected, Biden would be 86 by the end of his second term in office. Republican Ronald Reagan, who had the prior record as oldest U.S. president, ended his second four-year term at age 77 in 1989.

Trump, the frontrunner for the Republican nomination to challenge Biden in the 2024 election, is 77.

In a mid-September Reuters/Ipsos poll, voters expressed concern over Biden’s age and his fitness for office. Seventy-seven percent of respondents, including 65 per cent of Democrats, said Biden is too old to be president, while just 39 per cent said Biden was mentally sharp enough for the presidency.

By comparison, 56 per cent of poll respondents said Trump is too old for the office, while 54 per cent said he was mentally sharp enough to handle the challenges of the presidency.