Donald Trump serves McDonald's fries in latest US election ...

Donald Trump has taken his US presidential election campaign to a McDonald's in Pennsylvania, where he served fries to voters and answered questions from reporters through a drive-through window.

An employee at the fast food restaurant in Feasterville-Trevose, in Philadelphia's north-eastern suburbs, showed the Republican nominee how to dunk baskets of fries into oil before he helped fill takeaway bags for customers.

The Republican presidential nominee spoke to voters and delivered takeaway orders to customers at a drive-through window. (AP: Evan Vucci)

"It requires great expertise, actually, to do it right and to do it fast," Trump said during the appearance.

"I do appreciate it a little more. You say, 'give me French fries', I'll never forget this experience."

The store's owner, Derek Giacomantonio, told reporters he accepted Trump's request to visit because he wanted to show the "transformative working experience that one in eight Americans have had: a job at McDonald's".

The store's owner accepted Trump's request to visit so he could demonstrate the working experience of his staff. (AP: Doug Mills/The New York Times)

"It is a fundamental value of my organisation that we proudly open our doors to everyone who visits the Feasterville community," he said.

Local police closed the busy streets around the McDonald's — which CNN reported was closed for the event — as crowds gathered, passing motorists honked their horns and Trump supporters waved flags, held signs and took pictures.

Large crowds of Trump supporters and local residents gathered outside the store to wave flags, hold signs and take photos of the former president. (AP: Evan Vucci)

The visit came as Trump stepped up his criticism of Kamala Harris and dug into his claim — spread without offering evidence — that she never worked at the fast-food chain while in college, despite saying so during her campaign.

It's the latest example of the former president's longtime strategy of questioning the credentials of his political opponents by promoting baseless claims.

Trump worked with McDonald's employees during the store visit and said it "requires great expertise" to serve fries. (AP: Doug Mills/The New York Times)

Ms Harris says her experience working for McDonald's shows she understands working-class struggles.

"Part of the reason I even talk about having worked at McDonald's is because there are people who work at McDonald's in our country who are trying to raise a family," she said in an interview last month.

Trump also held an impromptu press conference with reporters through the McDonald's drive-through window. (AP: Evan Vucci)

The Democratic nominee spent Sunday celebrating her 60th birthday by meeting with Black voters in another election battleground state, Georgia.

Supporters at a Baptist church near Atlanta serenaded Ms Harris with a Happy Birthday song before she delivered a speech urging Americans to vote and "shine the light in moments of darkness".

ABC/wires