Tyson Fury has offered to quit on his stool if he fails to KO Anthony Joshua inside three rounds.
The heavyweights are due to clash in Saudi Arabia this summer to crown the division’s first undisputed world champion since Lennox Lewis in 1999.
Promoter Eddie Hearn insists an announcement is due imminently to confirm the fight will take place in late July or early August.
Ans Fury is so confident he will stop his rival early, he claims he is willing to throw in the towel after nine minutes.
Speaking on Instagram, Fury said: “While I’m on a rant I might as well call out one more person. A big useless dosser; not a real fighting man, a hype job, bodybuilder, cross fit, big ugly s**house, that’s Anthony Joshua.
“AJ, if you’re out there lets make this fight happen you big dosser, you big s***house bum dosser, I’m going to smash your face in too and there’s not oner thing you can do about it. Prove me wrong sucker, prove me wrong; I’m number one.”
He later added: “I’ve just been thinking… AJ, if you go past three rounds with me I’ll quit in the corner, that’s how confident I am of taking you out in the first two or three rounds. Out, out like a light.”
Fury and Joshua signed a contract last month for a two-fight deal but at that stage did not know when or where the first instalment would be staged.
They have both since agreed to host the fight in Saudi Arabia on either July 24, 31 or August 7 with the state offering a $150million site fee to be split between the heavyweight rivals.
But a row has broken out between the teams over whether the offer from the Middle East will translate into a signed agreement.
Fury’s promoter Bob Arum claims the offer is “a mirage” and accused Hearn of failing to deliver.
But Joshua’s representative insists a deal is close and that the fight will take place this summer as promised.
A second fight is then expected to take place in the UK in December with the winner of the first bout earning 60 per cent of the purse.