Fox News host Tucker Carlson has claimed that President Joe Biden takes 'pills' to boost his cognitive performance before public appearances. 

Biden, 79, has strenuously rejected similar allegations in the past, but Carlson claimed on his Friday evening show that he had spoken 'directly' to a witness who saw the alleged medication on the 2020 campaign trail.

'His staff, supervised by Dr. Jill, his wife, was giving him pills before every public appearance. Checking the time, and at the certain hour giving him a dose of something,' said Carlson.

'Before taking the medications, this person said Biden was 'Like a small child.' You could not communicate with him, he changed completely because he was on drugs and he clearly still is on drugs,' the pundit alleged.

Carlson's unproven allegation came during a lengthy monologue in which he argued that Biden is 'incapacitated' and suffering from 'dementia.'

A White House spokesperson did not immediately respond to an inquiry from DailyMail.com late on Friday. 

According to the latest report from his White House doctor, Biden takes prescription medication for an irregular heartbeat, high cholesterol, and seasonal allergies. 

None of those medications are considered cognitive enhancers. 

White House Physician Kevin C. O'Connor did not mention any cognitive issues in the November report, and wrote that Biden 'is fit to successfully execute the duties of the Presidency.'