Contracts have been signed for Britain's Fury and Ukraine's Usyk to fight for their combined titles on a date yet to be decided in Riyadh.

"They want to put Usyk-Fury, Joshua-Wilder on the same night. That might not happen until April," Joshua told reporters ahead of the US Formula One Grand Prix in Austin, Texas.

"When Fury gets through Ngannou, it is going to be late October, early November, so I doubt he will now prepare for Usyk and fight in December, it's too short," said the Briton.

WBC champion Fury is due to fight former UFC heavyweight champion Francis Ngannou in Saudi Arabia on Oct. 28 in a bout with professional boxing rules.

Usyk holds the WBA, WBO, IBF and IBO belts and, like Fury, has an unbeaten record.

"The next window (after that for Fury-Usyk) will probably be in March-April, so that's probably when the undisputed fight will potentially happen," said Joshua, who was in Austin after being announced last week as an investor in the Renault-owned Alpine team.

"Then obviously what we are being told is they want to make it a mega card and they like the sound of Joshua versus Wilder on the same card."

Wilder was WBC heavyweight champion from 2015 to 2020.

Joshua, twice beaten by Usyk, said his next fight would be in December and likely in London against a 'non-championship' opponent yet to be decided.

No date has been set for him to fight Wilder.

"Some fighters want to maximise their revenue," said the Briton. "It is like, 'where can we get the most money for the fight?' And they want to go to Saudi Arabia so they are waiting for the undisputed fight."