Donald Trump vowed Thursday to "crush" Joe Biden in the 2024 election, warning in his first campaign stop since his successor entered the 2024 race that the United States will descend into "anarchy" if the Republican billionaire isn't returned to office.

The defiant address at a hotel in Manchester, New Hampshire, came with the twice-impeached former president's legal woes multiplying, as a writer who accuses Trump of rape testified for a second day at a civil trial in New York.

"The choice in this election is now between strength or weakness, between success or failure, between safety or anarchy, between peace or conflict, and prosperity or catastrophe," Trump told a relatively-modest crowd of around 1,500 supporters.

"We are living in a catastrophe. With your vote on November 5, 2024, we are going to crush Joe Biden and the White House... at the ballot box, and we are going to settle our unfinished business."

It was Trump's first appearance since January in the Granite State, which propelled him to victory in the 2016 Republican nominating contest after a shaky start in Iowa.

Biden, 80, announced Tuesday he would seek a second term in 2024, warning that the next election, like the last, would be a "battle for the soul."

Many top Republicans say Trump, 76, is positioning himself to lose again after leading Republicans to poor showings in the 2020 general election and in the last two midterm cycles.

"Republicans want someone who can win in November of '24. Donald Trump is a loser," New Hampshire Governor Chris Sununu, who is said to be mulling a rival presidential bid, told NBC on Sunday.

Nine Republicans in the US Senate have endorsed the billionaire, but others are warning that prosecutions enmeshing Trump might undermine their hopes of taking the upper chamber of Congress back from the Democrats next year.

Trump is being sued for battery and defamation in civil proceedings in New York, accused of raping writer E Jean Carroll in 1996, and has been indicted over a 2016 hush money payment to a porn star in a criminal case likely to stretch well into election year.

He also faces the possibility of charges from the Department of Justice and Georgia prosecutors in cases involving his attempts to overthrow the 2020 election and his hoarding of government documents.

Yet Trump has consistently maintained double-digit leads in Republican primary polling, running far ahead of his nearest likely rival, Florida Governor Ron DeSantis, whom he described in his New Hampshire speech as "crashing and burning."

Trump, who denies all wrongdoing, angrily denounced the "endless witch hunts" against him, as he invariably does in public remarks, and told supporters he was retiring the "Crooked" nickname he uses to smear longtime foe Hillary Clinton and giving it to Biden instead.