Several doctors have called for US President Joe Biden to undergo cognitive testing, after a string of recent blunders.
It also comes after the US Justice Department released a report on Friday, which was scathing about Biden's health and his mishandling of classified documents. No criminal charges were filed.
Special counsel Robert Hur's report called Biden a "well-meaning, elderly man with a poor memory". It also said he couldn't remember when he was Vice-President, or when his son Beau died of glioblastoma.
On Friday, an outraged Biden hit back.
"I know what the hell I am doing," he told reporters. "My memory is fine."
Seconds later, he referred to Egypt's President Abdel Fattah El-Sisi as the leader of Mexico.
And in the past week, Biden has referred to dead leaders, mistaken countries for one another, and appeared to forget Hamas' name.
Some doctors have since called for Biden to take cognitive tests and prove he's fit for the role.
Dr Stuart Fischer, a physician from New York, told the Daily Mail the President has "got to be able to produce".
He said it may simply be mild impairment, but tests will give concrete evidence.
"If you want to prove to the public, you've got to show them."
Former US President Donald Trump was also under the same pressure in 2018, when critics called for his impeachment, saying he wasn't mentally fit for office.
Dr Jane Orient, an internal medicine physician from Arizona, told the Daily Mail she was concerned after seeing Biden's gaffes.
"The person who is commander in chief of our armed forces and making very critical decisions about every second of our life may not know what he's doing."
Dr Yusuf Hameed, an anaesthesiologist from Georgia, said mental decline happens to everyone, but some dementia symptoms have a faster onset.
"It's hard to delineate those patients who will have accelerated signs of dementia, but remembering conversations with dead world leaders is concerning," he told the Daily Mail.
Last week, Biden confused current French President Emmanual Macron with the late President François Mitterrand.
He also spoke about former German chancellor Helmut Kohl, who died in 2017, when he meant to say former chancellor Angela Merkel.
Dr Kenneth Heilman, a neurologist from Florida, said the only way to see if Biden's cognition is declining is to do a "full evaluation".
He said that involves speaking to them for a while, analysing their language, and if they have problems with finding words or understanding then it's a concern.
The Democratic Party now has a tough choice on its hands as it nominates a presidential candidate for the 2024 US elections.
Biden is the oldest sitting president in US history.
