Kamala Harris called Donald Trump a "fascist" Wednesday and warned that her US election rival was "increasingly unstable" as she addressed his reported praise for Adolf Hitler at a town hall event.

The Democrat`s fierce criticism came as she answered voters` questions on Trump`s suitability for office and past remarks at the CNN-hosted event in must-win Pennsylvania.

Acknowledging voters` concerns on a variety of top election issues, the vice president said: "They also care about our democracy and not having a president of the United States who admires dictators and is a fascist."

Trump`s political instincts were already the main topic of discussion following revelations from his longest-serving chief of staff, John Kelly, about the Republican`s praise for the Nazi dictator and his military in World War II, reports AFP.

The decorated Iraq veteran told The New York Times that Trump remarked that "Hitler did some good things too" and that instead of the US military, he "wanted generals like Adolf Hitler had."

With Trump`s rivals raising concerns about his willingness to honor American democracy, Kelly also repeated his warning that he believes his ex-boss "certainly falls into the general definition of fascist."

At her prime-time CNN event, Harris cited numerous former Trump administration officials, including his national security advisor and vice president, who have warned that Trump should not be returned to office.

"They have said explicitly he has contempt for the Constitution of the United States," she said. "They have said he should never again serve as president of the United States."

She added: "I believe Donald Trump is a danger to the wellbeing and security of America."

Trump -- who declined to appear in his own CNN town hall -- hit back at a rally in Georgia, a key swing state the 78-year-old Republican won in 2016 and then narrowly lost to President Joe Biden four years later.

He attacked Harris over her economic policy and dusted off his catchphrase from his days on NBC reality TV show "The Apprentice" as he exhorted the crowd in Duluth to tell Harris: "You`re fired!"

"You have to stand up and you have to tell Kamala Harris that, `Kamala, you`ve done a horrible job. You`re the worst ever. There`s never been anybody like you... Kamala, you`re fired. Get out,`" he thundered.

- Trump accused -

Moments before Trump was due onstage, The Guardian newspaper reported a former model`s allegations that he groped her after the two were introduced by sexual abuser Jeffrey Epstein in the 1990s. He did not address the claim at any point during his speech.

Harris, 60, touched down in Pennsylvania ahead of the town hall near Philadelphia, stopping at the Famous 4th Street Delicatessen to fist-bump employees and take selfies with patrons.

"Knock wood, God willing, we are going to win," she said to cheers.

Some 26.5 million Americans have already voted by mail or in person, more than a million of them in Pennsylvania.

The Keystone State is a coveted prize for the candidates, and Harris and Trump have made repeated appearances there and across other swing states that decide US elections.

With polls suggesting a tight election in its final stretch, Harris has unveiled plans for a "closing argument" rally on Tuesday at the Washington site where Trump addressed supporters before they stormed the US Capitol on January 6, 2021.

The Harris camp has also confirmed that Michelle Obama will join her at an event Saturday in battleground Michigan, the former US first lady`s debut campaign stop with Harris.

It will follow Harris`s first campaign appearance with former president Barack Obama, on Thursday in Georgia`s largest city Atlanta, as part of a major Democratic get-out-the-vote effort.

Veteran rocker Bruce Springsteen is set to kick off the event with a concert.

Harris`s sudden entry into the election campaign in late July shook the country, which was expecting a rematch between Biden and Trump, now a felon convicted on 34 charges of falsifying business records to hide hush-money payments to a porn star.

While Trump hammers home his promises of a migrant crackdown and economic good times after a period of high inflation, the Harris campaign has targeted his mental and physical fitness for the Oval Office while she courts moderate Republican voters.