Washington DC - President Joe Biden took aim Wednesday at Donald Trump, joking that when his rival famously remarked about injecting bleach to tackle Covid it instead went in his much-discussed hair.

"Remember when he was trying to deal with Covid... He suggested just inject a little bleach in your veins," Biden said at a construction workers event in Washington.

"He missed, it all went to his hair!" the Democrat quipped, eliciting a burst of laughter among the audience at North America's Building Trade Union, which has endorsed the 81-year-old in this year's election.

Biden made a similar gag on social media this week as he shared a video clip of Trump's infamous comment that he made at a White House press conference four years ago on April 23, when he was president.

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"Don't inject bleach. And don't vote for the guy who told you to inject bleach," Biden wrote on X, formally Twitter.

The political rivalry between Biden and Trump has delved into personal animosity as election campaigning heats up.

Trump (77) regularly mocks his opponent's lifelong stutter and calls him "sleepy Joe."

Meanwhile, Biden has picked on Trump's financial troubles, dubbing him "broke Don" in reference to his legal battles, including the alleged falsifying of business records to pay hush money to porn star Stormy Daniels.