"I Promise You, I'm OK": Biden Tells Supporters Amid Series Of Gaffes

US President Joe Biden returned to the campaign trail Friday seeking to reassure voters and Democrats alike about his fitness for office, after a major news conference failed to silence calls for him to quit.

"We've got to finish the job. And I promise you I am OK," the 81-year-old told supporters at a diner in Northville in the battleground state of Michigan, which he must win in November to beat Donald Trump.

Biden was to give a speech later in Detroit warning of the "nightmare" of a second Trump term under a hard-right manifesto that his campaign is pinning to the former president.

But the drumbeat of Democrats urging Biden to step aside kept getting louder, with 19 lawmakers having now openly called on him not to seek reelection following a disastrous debate performance against Trump on June 27.

The bloodletting continued despite a defiant Biden insisting in a high-stakes press conference at a NATO summit in Washington on Thursday that he would run again, and win.

A series of gaffes, including referring to Vice President Kamala Harris as "Vice President Trump" and mixing up Ukrainian President Volodymyr Zelensky with Russian strongman Vladimir Putin, kept the focus on his mental acuity.

- 'Gaffes for 40 years' -

"The president understands that there's still some anxiety," Biden campaign communications director Michael Tyler told reporters traveling to Michigan with the president aboard Air Force One.

"That's why he's laser focused on demonstrating that he is the best person to take on Donald Trump and defeat him in November."

Tyler played down the verbal slip-ups, saying Biden has been known for making them throughout his long political career.

"Joe Biden has been making gaffes for 40 years, he made a couple of last night, he probably will continue to do so," he said.

As the row sparked by the debate enters a third week, Biden has been making efforts to reach out to lawmakers, speaking by telephone to Latino and Asian members of the House of Representatives on Friday.

The top Democrat in the House of Representatives, Hakeem Jeffries, meanwhile said he had met with Biden late Thursday after the press conference.

Jeffries said he "expressed the full breadth of insight, heartfelt perspectives and conclusions about the path forward" but did not give further details.

- 'Complete losers' -

The campaign event in Detroit is Biden's fourth trip this year to the state, part of the industrial "blue wall" along with Wisconsin and Pennsylvania that were key to his 2020 win against his rival.

Biden's speech is expected to focus on "Project 2025", a blueprint for power by hardline conservatives that Democrats have said the former president would implement, despite the 78-year-old's denials.

"Project 2025 is run and paid for by Trump people," Biden was to say according to excerpts released by the campaign.

"And here is the nightmare it would unleash."

The concerns over Biden are affecting Democratic donors, with Hollywood star and high-profile supporter George Clooney calling on Biden to step aside on Wednesday.

A number of other key donors have told the largest Biden campaign fund that around $90 million in pledged donations is on hold if he carries on running, the New York Times reported on Friday.

Trump, who mocked Biden on social media during the news conference, followed up on Friday by saying the Zelensky gaffe was "unpardonable."

But he added that Biden "shouldn't allow complete losers like George Clooney, under the total auspices and control of Barack Hussein Obama, to push him out of office. That must be his decision, and his decision alone."

Trump was referring to reports in US media that some in Biden's camp believe former president Obama, under whom Biden served as vice president, is involved behind the scenes with the rebels.

(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)