Former US President Donald Trump, fresh off his third appearance in court as a criminal defendant, delivered a speech full of defiance and bluster on Friday night, insulting prosecutors and declaring that the charges he faces only help his 2024 presidential campaign.

"Any time they file an indictment, we go way up in the polls," Trump said at a Republican Party dinner in Alabama. "We need one more indictment to close out this election. One more indictment and this election is closed out. Nobody has even a chance."

Trump pleaded not guilty on Thursday to crimes related to his efforts to overturn the results of his 2020 election loss. Although it is his third criminal indictment this year, this case is the most serious, with the federal government he once ran charging him with orchestrating a scheme to block the peaceful transfer of power.

But Trump was characteristically unapologetic as he took the stage on Friday night to Lee Greenwood's God Bless the USA, flashing a thumbs-up at the crowd, raising his fist and taking in a standing ovation of nearly three minutes.

"We are gonna be here for a little while," he joked, asking the crowd to take a seat.

The latest set of charges focuses on the two months between his November 2020 loss to Democrat Joe Biden and the January 6, 2021, insurrection at the US Capitol. Trump has denied wrongdoing and wedded his 2024 presidential campaign to his legal defence and his false claims of 2020 election fraud.

In a sign of that defiance, his campaign released an online ad on Friday attacking the justice department special counsel Jack Smith, who led the investigation that resulted in Trump's latest charges and a separate case where he is charged with mishandling classified documents.

The ad, which is expected to start airing on television next week, also attacks Manhattan district attorney Alvin Bragg, who has charged Trump in a hush-money case, and Fulton county district attorney Fani Willis, who is believed to be close to filing charges in her investigation into efforts by Trump and his allies to overturn the 2020 election results in Georgia.

A Trump aide said the ad will start airing on Monday and Tuesday in Washington DC, New York, Atlanta and on national cable. The ad was also shown to the crowd at the Alabama dinner on Friday night.

Trump has continued to receive endorsements from Republican officials throughout the investigations and cases.

AP/PTI