Washington DC - President Joe Biden has forcefully denounced Donald Trump's response to his conviction on 34 felony charges in his hush money criminal trial.

"It's reckless, it's dangerous, it's irresponsible for anyone to say this is rigged just because they don't like the verdict," Biden said at the White House on Friday in his first public comments on the historic verdict.

"Our justice system has endured for nearly 250 years, and it literally is the cornerstone of America, our justice system," Biden said. "The justice system should be respected. And we should never let, never allow anyone to tear it down.

"Donald Trump was given every opportunity to defend himself," Biden said of his Republican election rival, noting that he would now have the opportunity to appeal the verdict.

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It is unusual for Biden, a Democrat, to so directly comment on Trump's legal troubles, usually preferring to steer clear of the controversy engulfing his predecessor at any given moment.

Polls show the two locked in a tight race at the national level, and analysts say even slight shifts in support could prove decisive come November 5.

Trump earlier vented his anger about the judgment rendered against him in New York. He was convicted on all counts of falsifying business records to cover up a hush money payment to a porn star in the waning days of the 2016 election campaign.

In a statement at Trump Tower in New York, he repeated the accusation that the trial was politically motivated and "rigged."

He also insulted the judge and his political opponents, calling Biden "the dumbest president we've ever had."