Tyson Fury has warned Deontay Wilder "I'm not gonna wait forever" amid uncertainty over a trilogy fight.
Wilder has the right to a third bout with Fury after the Briton won their rematch at the MGM Grand in February to claim the WBC title.
December 19 had been talked of as a potential date for their next battle, but no agreement has been reached and Fury's promoter, Frank Warren, said the 32-year-old is not prepared to wait until next year to step into the ring with Wilder again.
With Dillian Whyte able to enforce a mandatory fight for the WBC heavyweight title if he beats Alexander Povetkin on Saturday, Fury is running out of patience with Wilder.
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He posted on Instagram on Thursday: "@bronzebomber where you at mush? The clock is ticking!! I’m not gonna wait for ever!!!
"There is other bums in the division that I want to eat for breakfast."
It was revealed in June that Fury and IBF, WBA and WBO champion Anthony Joshua had agreed terms for a two-fight deal.
Joshua was due to put his titles on the line against Kubrat Pulev on June 20, but the fight was postponed due to the coronavirus pandemic.
Warren told The Telegraph last week: "Tyson is the fans' favourite and the most famous boxer in the world. I want the best for him. I want him to come away from this sport having been the best of his generation. He has to fight Anthony Joshua."
Warren added: "We talk about the Dillian Whyte fight and all the rest but AJ is the only fight fans are praying for. The fight the fans want is those two facing each other.
"That fight should be in the UK and we should be moving heaven and earth to make it work here. I don't want to take that fight on the road.
"Kubrat Pulev has got a contract to fight Joshua and Tyson will fight this year, but the fight after that should be AJ.
"I hope it's for the four belts, but if it's not, it's not. The belts are fantastic, but if that gets in the way of making the fight happen then forget the belts. At the end of the day, fans will be buying tickets to see these two fighters meet, not the belts."