BBC:
The White House has fought back against questions about Joe Biden’s mental fitness, with the US president telling anxious fellow Democrats it is time to end the criticism, and daring doubters in the party to challenge him.
In a tense news conference, the president’s spokeswoman rejected suggestions that he might be suffering from an undisclosed illness.
Mr Biden, 81, himself took the unusual step of calling in to MSNBC’s morning show, saying: “I am not going anywhere.”
Questions about his mental acuity have intensified since a poor debate performance against Donald Trump on 27 June.
The scrutiny is unlikely to fade this week as he hosts a summit in Washington for leaders of Nato countries.
In Monday’s daily press conference, White House press secretary Karine Jean-Pierre rejected speculation that Mr Biden was being treated for Parkinson’s disease, which can cause stiff movement and slurred speech.
“Has the president been treated for Parkinson’s?” she said. “No. Is he being treated for Parkinson’s? No.”
An expert on Parkinson’s disease from Walter Reed National Military Medical Center near Washington DC has visited the White House eight times since last year, the New York Times reports.
But White House records show the same doctor also made a number of visits during the Obama administration from 2012-16.
Ms Jean-Pierre would not comment on the matter, citing the need to protect the privacy of the doctor and security reasons.
On Monday, the president called in to left-leaning MSNBC’s Morning Joe programme, laying down the gauntlet to critics to “challenge me at the convention” next month, or rally behind him against Trump.
In a letter sent to congressional Democrats also on Monday, Mr Biden said he “wouldn’t be running again if I did not absolutely believe” that he could beat Trump, the Republican challenger in November’s election.
