Mr Biden's was responding to a question from Howard Stern during an hour-long interview on satellite radio network SiriusXM.

"I am happy to debate him," he said. "I am, somewhere. I don't know when."

Trump campaign adviser Chis LaCivita responded on X/Twitter: "Ok, let's set it up!"

Traditionally, election-year presidential debates have been organised by a nonpartisan commission and scheduled in the autumn.

Last November the commission announced the three 2024 presidential debate locations - at universities in Texas, Utah and Virginia - with dates set for September and October.

Mr Biden had not committed to those debates before his remarks on Friday, saying in March that his willingness to appear on a stage with Mr Trump "depends on his behaviour".

The president's comments on Friday came with no advance notice from his campaign and may have been made off the cuff.

In recent weeks, Mr Trump and his campaign representatives had been pressing Mr Biden to debate earlier and more often than those scheduled by the debate commission.

At a campaign rally in Pennsylvania, Mr Trump appeared on stage near an empty lectern displaying a placard that "anytime, anywhere, anyplace".

Mr Trump's tactic represents somewhat of a reversal, as both he and Republican officials had previously accused the debate commission, which also selects debate moderators, of being biased in favour of Democrats.

The Republican National Committee withdrew its involvement with the debate commission in April 2022, raising doubts about whether the Republican nominee would participate in 2024.

The former president declined to appear at any of his party's five primary debates this election cycle, held between August and January, pointing to his polling lead as evidence that Republican voters clearly supported his campaign and that debates were not necessary.

He went on to win all but one of the Republican nomination contests and became the party's presumptive nominee by March.Mr Biden and Mr Trump debated twice during the 2020 presidential campaign.

The first was particularly contentious, with the then-president frequently interrupting Mr Biden and debate moderator Chris Wallace of Fox News.

A third debate was scheduled, but Mr Trump withdrew after it was changed to a virtual event because of Mr Trump's coronavirus diagnosis, which came shortly after the second debate.

The first televised US presidential debate was held between Richard Nixon and John F Kennedy in 1960 and is largely credited with helping Kennedy win the White House.

Thea two major party candidates have debated at least once every presidential election year since 1976.

By Anthony Zurcher,North America correspondent