Florida Governor Ron DeSantis says he will seek the 2024 Republican nomination for president, setting up a showdown with his one-time ally, former US president Donald Trump, that will shake up the race for the White House.

DeSantis, 44, made the announcement in a video ahead of an audio interview on Twitter with its CEO, Elon Musk.

“We need the courage to lead and the strength to win,” DeSantis said. “I’m Ron DeSantis, and I’m running for president to lead our great American comeback.”

His long-expected foray changes the shape of the contest for the Republican nomination, as he immediately becomes Trump’s biggest rival.

The nominee will face US President Joe Biden, a Democrat, in the November 2024 general election.

In the weeks leading up to his presidential bid, DeSantis has toured the country, visiting states such as Iowa and New Hampshire that will hold early nominating contests.

He has boasted of his record as Florida’s governor, including his battles with the federal government over pandemic policies.

His decision to wait until now to jump in has given Trump space to batter DeSantis with a series of attacks, costing the governor standing in polls and frustrating some allies who might have preferred DeSantis step into the ring earlier.

A pro-Trump Super PAC called MAGA Inc has already spent more than $US14 million ($A21 million) on television ads and other media attacking DeSantis, according to disclosures to the Federal Election Commission.