Former Vice President Joe Biden Joe BidenBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Democratic groups using Bloomberg money to launch M in Spanish language ads in Florida Harris faces pivotal moment with Supreme Court battle MORE's campaign team fired back at a tweet by President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE describing Biden as "a low IQ individual," calling it "unhinged and erratic."

“I would say the tweet speaks for itself, but it’s so unhinged and erratic that I’m not sure anyone could even say that with a straight face," an unnamed aide told ABC News. “The spelling error was not the main problem with the first one.”

Trump tweeted on Saturday that he has "confidence" in North Korean leader Kim Jong Un Kim Jong UnSatellite images indicate North Korea preparing for massive military parade South Korea warns of underwater missile test launch by North Korea Trump says he didn't share classified information following Woodward book MORE despite recent missile tests some have said violate a United Nations resolution. In the same post, Trump said Kim "called Swampman Joe Biden a low IQ individual."

"North Korea fired off some small weapons, which disturbed some of my people, and others, but not me. I have confidence that Chairman Kim will keep his promise to me, & also smiled when he called Swampman Joe Biden a low IQ individual, & worse. Perhaps that’s sending me a signal?" Trump wrote.

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In his first version of the tweet, Trump misspelled Biden's name as "Bidan."

Trump and Biden have exchanged more barbs in recent days as the 2020 presidential race heats up and as Biden appears to be the leading Democratic candidate.

Last week, Trump attacked Biden during a campaign rally, arguing that foreign countries want Biden to become president so they can keep "ripping off" the U.S.

"He announced he’s running for president, and he said it’s because foreign leaders called him up and begged him to do it," Trump said. "Absolutely. Foreign countries liked it much better. That’s what they want. They want Biden so that China can continue to make $500 billion a year and more, ripping off the United States."