Anthony Joshua has branded heavyweight rival Tyson Fury a "fraud" as their blockbuster unification showdown appears on the brink of collapse.

Joshua, the IBF, WBA and WBO champion, and Fury, who holds the WBC belt, have been in negotiations over a fight to crown the undisputed ruler in the division.

Promoter Eddie Hearn said he expected to announce an August 14 showdown, to take place in Saudi Arabia, this week, but Deontay Wilder – who Fury sensationally deposed last year – has derailed plans.

Wilder won an arbitration hearing on Monday that recognised his contractual right to a third bout with Fury, with whom he shared a thrilling 2018 draw before suffering a first career loss via seventh-round stoppage in February 2020.

Fury's promoter Bob Arum told ESPN that Fury-Wilder III has been provisionally booked at Allegiant Stadium in Las Vegas for July 24, stating step aside payments were not an option.

"It's better to get rid of [Wilder] and go about our business. We can make the Fury-Joshua fight for November or December," he said.

Joshua, who might now face his WBO mandatory challenger and former undisputed cruiserweight champion Oleksandr Usyk, expressed frustration that the Fury fight came so close to fruition before hitting a stumbling block, accusing his fellow Briton of using the whole episode as a publicity stunt.

He tweeted: "@Tyson_Fury the world now seen you for the fraud you are. You've let boxing down!

"You lied to the fans and led them on. Used my name for clout, not a fight. Bring me any championship fighter who can handle their business correctly."

Fury was typically strident in his response, proposing a fanciful bare-knuckle bout with Joshua for a combined £40million.

"Your (sic) more full of s*** that (sic) Eddie. Spouting absolute s****. Your team knew there was an Arbitration going on, it was out of my hands!

"But I tell you what if I'm a fraud let's fight this weekend bar (sic) knuckles till 1 man quits? Let's put up 20 mill each."

The barbs continued, with Joshua saying, "I'll slap your bad head and you'll do nothing" and Fury labelling his countryman a "dosser" a "bum" and a "bottle job".

Fury became a two-time world heavyweight champion when he stopped Wilder and remains undefeated in 30 professional fights, with 29 wins and a draw.

His first title victory came when he out-pointed long-reigning unified champion Wladimir Klitschko in 2015 before spending time away from the ring due to personal problems.

Joshua duly collected the IBF, WBA and WBO titles with wins over Charles Martin, Klitschko and Joseph Parker respectively.

He lost those belts in a shock stoppage loss to Andy Ruiz Jr in June 2019, a sole professional defeat that he avenged in a rematch before the end of that year.