Tyson Fury has told Anthony Joshua to “grow a set of nuts” and urged his fellow British heavyweight to do his talking in the ring.

While there remains little prospect of Fury and Joshua reaching a deal to fight this year, they have continued to spar in public. Fury, who will make his ESPN debut when he looks to hand the unheralded Tom Schwarz his first defeat in 25 fights in Las Vegas on 15 June, bristled at suggestions he is using his meeting with the 6ft 5in German as a preparation for a future bout with Joshua. He could barely hide his disdain after being told of the height similarities between Schwarz and the 6ft 6in IBF, WBA and WBO champion.

“Joshua is in my rear-view mirror,” Fury said. “He’s stuck in a certain year. The big fights ain’t happening for him. He needs to grow a set of nuts and step up to the plate instead of talking about fighting the heavyweights. People are sick of hearing all the same stuff with him. Grow up and fight somebody.

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“You have to prove yourself in the boxing ring. That’s how boxing works. I’ve had to prove myself time and time again. Step up and fight somebody. That’s how the cookie crumbles. I’m fighting tall people because we are all tall in the heavyweight division.”

Fury’s deal with ESPN has him promoted by Top Rank’s Bob Arum alongside Frank Warren and it has derailed attempts to stage a rematch with Deontay Wilder, who has a deal with the network Showtime. Wilder defends his WBC title in Brooklyn on 18 May against Dominic Breazeal.

Yet despite the boxing community’s disappointment at Fury choosing to take on Schwarz, he did not hold back in his criticism of Joshua, whose fight against Andy Ruiz Jr will be shown in the US on the streaming service DAZN on 1 June.

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“Maybe it’s a lack of self-belief, to actually be able to believe you can beat these top men,” he said. “When I came back after three years out of the ring, not for one minute did I believe any of them could ever beat me and I proved that by having a few months of training and jumping straight in with Wilder.”

Arum believes there is more chance of striking a deal with Wilder’s camp than Joshua’s following Fury’s controversial draw with the American last year. “I think it’s going to be Wilder first and I think it will be some time next year,” the veteran American promoter said. “We’re further along with Wilder than with Joshua. If it’s pay per view it has to be in the US.”

However Arum added he wants Fury to fight Joshua, even though there would be no place for DAZN in the US. “If the public won’t support the guy or organisation preventing something happening they can force it in a second by not giving them money,” he said. “I’ll make it happen.”

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Arum aims to make the American public fall in love with Fury. He talked about a guest appearance on Jimmy Kimmel’s show, compared the Gypsy King to Muhammad Ali and said he wants to turn him into the next George Foreman.

“You see George all over television to this day, selling insurance, selling people a place where they can register inventions,” Arum said. “He’s all over television. Forget that he made a quarter of a billion dollars off the Foreman Grill. That type of thing is available to Tyson Fury.”

Fury said his focus is on his next fight. “When you go there and you want to become a celebrity, which I have no interest in at all, and you overlook what you do for a living, you end up getting chinned. I’d rather win all my fights than be a celebrity. What motivates me is the Ws. It’s not the suits or the fast cars.”

Tyson Fury takes on Tom Schwarz live on BT Sport Box Office, Saturday 15 June. For more information go to www.bt.com/btsportboxoffice