Kamala Harris turned 60 on Sunday in the final stretch of a knife-edge US election, making campaign stops at Black churches in Georgia as her 78-year-old opponent Donald Trump served fries at a Pennsylvania McDonald's in a bid to earn working-class credibility.

Throughout the day Harris lambasted Trump's increasingly disparaging, dark language on the trail, saying in an interview on MSNBC that Americans "deserve so much better."

"Donald Trump should never again stand behind the seal of the president of the United States. He has not earned the right," Harris said.

Recently Trump has likened undocumented migrants to animals, threatened revenge against his perceived enemies, praised autocrats like Vladimir Putin of Russia and described America as a ruined nation only he can fix.

And over the weekend he used an expletive to describe Harris.

Speaking at a Baptist megachurch near Atlanta, the Democrat urged a Black congregation to embrace compassionate values while others "spread hate, sow fear and cause chaos."

She also appeared alongside Stevie Wonder, who sang Harris his rendition of "Happy Birthday" while urging voters to "think about more than yourself when you vote."

Georgia is among the key states expected to decide the November 5 election.

With just over two weeks before Election Day, the Democratic vice president and the Republican billionaire are in a fierce, split-screen race.

On Sunday Trump was all smiles as he scooped fries at a McDonald's franchise outside of Philadelphia, donning a black-and-yellow apron over his white shirt and red tie.

The campaign stop was intended as a jab at Harris, who has talked about working at the fast-food chain in her youth.

Trump has repeatedly said, without offering evidence, that Harris never worked at a McDonald's. A friend of Harris's told The New York Times she recalled her having worked there.

"I don't mind this job," said Trump during his brief stint as a server, at one point asking if customers ever ask for more salt.

"I love salt!" he exclaimed, also throwing some over his shoulder onto the floor, explaining that he is "superstitious."

Told by reporters that Sunday was also Harris's birthday, Trump wished her well.

"I think I'll get her some flowers," he quipped. "Maybe I'll get her some fries."

Both candidates are spending their final campaign days in pivotal states, as are their surrogates.

Tesla and SpaceX boss Elon Musk has been stumping for Trump, while Harris taps pop star power, with singers Lizzo and Usher making Saturday appearances for her.

Shawn Fain -- head of the United Auto Workers, one of the most influential unions in the country -- appeared in Pennsylvania on behalf of Harris, telling rural voters in the large battleground state that "Trump is bought and paid for by Musk" and that the Republicans can't simply buy support from working-class voters.

"The billionaires have the money. They can throw all the money they want in the election, but working-class people have the votes, and votes are the great equalizer in this fight," Fain said.

In the lead-up to her birthday, Harris increasingly raised questions about Trump's fitness to be president.

"He's ducking debates and canceling interviews because of exhaustion," Harris told an Atlanta rally Saturday, mocking his rambling, off-script speeches.

The former president has surprised attendees at his rallies with sometimes bizarre references, including a ribald reference to the anatomy of a famous golfer.

Trump on Sunday insisted his age wasn't slowing him down, telling a Pennsylvania town hall that "we've had some of the greatest leaders in world history that are in their 80s."

His age and spontaneous remarks have not appeared to be a deal-breaker for voters, as polls show a close battle ahead.

(AFP)

Harris celebrates birthday at Georgia churches as Trump serves McDonald's