Atlanta, Georgia - Donald Trump and President Joe Biden traded barbs at dueling rallies on Saturday as the race for the White House continues to heat up.

Biden stumped in the key state of Georgia as he sought support from African Americans.

The 81-year-old narrowly won Georgia in 2020 and some polls show Black voters are increasingly deserting him ahead of November's rematch with Trump.

"Our democracy is really on the line," Biden told supporters at Mary Mac's Tea Room, a Black-owned restaurant in Atlanta.

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"My opponent's not a good loser. But he is a loser," Biden said to applause. "He's clearly unhinged."

"Folks, Trump isn't running to lead America. He's running for revenge," the 81-year-old insisted, adding: "We cannot let this man become president. Our children's future is at stake... We have to win this race, not for me, but for America."

Meanwhile, in a rambling 90-minute address to the NRA, Trump said Biden is "the worst president in the history of our country by far" and suggested the Democrat was "full of bulls***."

"You're fired, get out of here, Joe!" he called out to laughter from the thousands-strong crowd in Dallas, Texas, where the NRA gave the 77-year-old its endorsement.

Trump, who is fending off multiple indictments for his unprecedented attempt to overthrow the results of the 2020 election, was twice impeached as president, and has been spending his weeks in a New York court as part of a criminal trial, told the crowd Biden is "crooked" and a "threat to democracy."

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"Our enemies want to take away my freedom because I will never let them take away your freedom," he told the crowd in Dallas.

"In the end, they're not after me. They're after you. I just happened to be standing in their way."