Biden turns 81 as age worries weigh on re-election

White House press secretary Karine Jean-Pierre told reporters on Monday that Biden and his family would celebrate his birthday later this week with coconut cake when they gathered for the Thanksgiving holiday on the island of Nantucket.

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

At a ceremony on Monday to pardon the National Thanksgiving Turkey, Biden joked he was not around for the first such turkey event 76 years ago.

"I want you to know I wasn't there at the first one. I was too young to make it up," he said.

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 US president, ended his second four-year term at age 77 in 1989.

Trump, 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 fitness for office.

Seventy-seven per cent of respondents, including 65 per cent of Democrats, said Biden was 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.

Jean-Pierre, asked about the poll results, said Biden has managed to mark some major legislative achievements and should be judged on his record, not his age.

"Our perspective is that it's not about age, it's about the president's experience," she said.

"We have to judge him by what he's done, not by his numbers."

Australian Associated Press