Oleksandr Usyk has pledged to enforce his WBO mandatory and challenge Anthony Joshua for the heavyweight title, potentially scuppering hopes of an all-British undisputed fight.

Joshua, who is due to face his IBF mandatory Kubrat Pulev later this year, has reportedly agreed terms with Fury to fight for all four heavyweight belts next year.

However, if Usyk’s mandatory is called by the WBO, Joshua will have no option but to either face the undefeated Ukrainian or vacate his belt.

“Usyk has been the WBO mandatory challenger for more than one year,” his co-promoter Alexander Krassyuk told Sky Sports. “He has agreed to let AJ versus Pulev happen, with regards that the winner fights him next. This statement is still solid.

“Our plan is A) beat Dereck Chisora B) push AJ to comply with WBO rules or vacate the title C) defeat AJ (or any other WBO champion or contender and become the heavyweight champion. Simple and practical.”

Usyk, a 2012 Olympic gold medallist, who was crowned undisputed champion at cruiserweight before moving up a division, is scheduled to face Britain’s Dereck Chisora later this year.

“According to our latest talks with Eddie, Usyk vs Chisora has to go at the end of October,” Krassyuk said. “Still much depends on `Covid-19 restrictions but we all want to make it happen.”

Speaking in the past about a possible fight against Usyk, Joshua said: “A very credible opponent. When I’m trying to build my record, I want opponents like Usyk to say that I’ve defeated them.

“He uses his feet very well, and positions his hands well. You can’t hit him because his feet move so well. If you do manage to catch him, [the punches] are brushing off the gloves.

“What I’d do, as I have done already, is study him – from his footwork, his hand positioning, to his openings. Then I’d go to former people who have faced him and find out information on how to defeat him.”