U.S. Republican presidential nominee Donald Trump has agreed to an offer from Fox News to hold a debate with Democratic U.S. Vice President Kamala Harris on Sept. 4, he said in a post on Truth Social late on Friday.

"Rules will be similar to the rules of my debate with Sleepy Joe, who has been treated horribly by his party, but with a full arena audience," Trump said, referring to President Joe Biden, who has since dropped his reelection bid.

The post was removed for a few minutes before being reposted, with Trump deleting his proposal for a "major" town hall gathering on the same date if Harris was "unwilling or unable to debate".

Harris had responded last month that she was "ready" after Fox News proposed the presidential debate between the two candidates on Sept. 17.

After Biden dropped out of the race on July 21 and backed Harris, Trump said he would not debate her because she was not the official candidate.

As proof of her lack of support, he added that former President Barack Obama had yet to endorse her. But Obama did so a day later, and on Friday, she secured the delegate votes needed to clinch the Democratic nomination.