Donald Trump says he has agreed to a proposal from US broadcaster Fox News to debate Vice-President Kamala Harris on 4 September.

A debate between the former president and incumbent Joe Biden had been scheduled on rival network ABC News for 10 September and Ms Harris agreed to take Mr Biden’s place in it.

But Mr Trump said the ABC debate had been "terminated" by Mr Biden leaving the race. Ms Harris is yet to comment on the new Fox News proposal.

The two candidates will go head-to-head for the presidency on 8 November, after Ms Harris was formally chosen as the Democratic nominee on Friday.

If the Fox News debate goes ahead, it will be the second presidential debate of the election cycle - and the first between Ms Harris and Trump.

It is pencilled to take place in Pennsylvania - a key battleground state - at a location yet to be decided. Trump wrote that the moderators would be Fox News’ Bret Baier and Martha MacCallum - and that the rules would be similar to his debate with Mr Biden.

"If for any reason Kamala is unwilling or unable to debate on that date, I have agreed with Fox to do a major Town Hall on the same September 4th evening," Mr Trump wrote on his social network Truth Social.

Mr Biden dropped out of the presidential race on 21 July, saying it was "in the best interest of my party and the country".

His decision followed weeks of speculation about his health after an incoherent debate performance against Mr Trump, and later gaffes during public appearances.

He threw his backing behind Ms Harris, who then won support from the Democratic establishment and was formally chosen as the Democratic nominee on Friday.

During a campaign rally in Atlanta on Wednesday, Ms Harris challenged Trump to debate her, saying “if you got something to say, say it to my face."