Biden tells Democrats he's not leaving the race, and it's time to stop talking about it

President Biden sent a two-page letter to Democratic lawmakers on Monday to say that “I am firmly committed to staying in this race," saying speculation over his future was helping former President Donald Trump — and that it was time to stop.

“The question of how to move forward has been well-aired for over a week now. And it’s time for it to end. We have one job,” Biden said.

Biden, 81, has been insistent that he would continue his campaign even after he badly faltered in a debate with Trump — a performance that alarmed Democrats worried about his ability to run, win and govern. He has said he had a cold and jet lag, and has been working since to try to demonstrate he is still up to the job.

Biden also spoke with donors on Monday

On Monday morning, he made an unusual live call in to MSNBC's Morning Joe and angrily defended his electoral and policy record. He angrily expressed his frustration with the Democrats who are questioning his stamina.

"I'm not going to explain anymore about what I should or shouldn't do — I am running," Biden said during the 20-minute conversation with the show's hosts.

"I don't care what those 'big names' think. They were wrong in 2020, they were wrong in 2022 about the red wave. They're wrong in 2024," Biden said.

He said he last had a neurological exam as part of his annual physical, which the White House disclosed in February.

Biden spoke with donors on a campaign call on Monday, and was preparing to speak with world leaders in Washington for the NATO summit this week. He is slated to hold a solo press conference on Thursday.

Biden dared would-be candidates to challenge him at the Democratic convention next month.

"Come on, give me a break. Come with me. Watch. Watch," he said, referencing voter support in recent campaign stops. "I'm getting so frustrated by the elites... in the party who 'they know so much more.' But if any of these guys don't think I should run, run against me. Go ahead. Announce for president. Challenge me at the convention."

In his letter, Biden said that Democratic voters had spoken during the primaries — and that it was their decision to make, “not the press, not the pundits, not the big donors.”

“This was a process open to anyone who wanted run. Only three people chose to challenge me. One fared so badly that he left the primaries to run as an independent. Another attacked me for being too old and was soundly defeated,” he said, apparently referring to Robert F. Kennedy Jr. and Rep. Dean Phillips, D-Minn., respectively.

NPR's Elena Moore contributed to this report .