WBC heavyweight title-holder Tyson Fury has labelled Oleksandr Usyk a “14-stone coward” after talks for their undisputed heavyweight title fight on April 29 broke down.

Sources told ESPN on Wednesday that the talks came to a standstill with the two parties unable to agree deal points beyond the agreed 70-30 revenue split in Fury’s favour. Sources added that Usyk shut down his training camp and will regroup with his team to plot his next fight.

In an explosive rant posted on Instagram on Thursday, Fury said: “You got your rematch and didn’t want to fight at that. You were never man enough to tangle with the Gypsy King ever in your life.”

He added: “[You] Tried all week to get out of it, begging for a rematch. You got your rematch, then didn’t even want to fight at that … You little 14 stone coward.”

In a joint radio interview with Fury’s promoter Frank Warren on Wednesday, Usyk’s promoter, Alexander Krassyuk said: There was a feeling that after Usyk accepted 70-30, Tyson Fury started thinking that he could put a saddle around his neck and start riding Usyk as much as he can. It’s not right. I mean, Usyk accepted the 70-30 split as a courtesy.”

The WBA is poised to order a fight between Usyk and Daniel Dubois, with the Englishman up first in the rotation system used for boxing’s unified champions unless a last-ditch effort can be made to save the bout against Fury.

“Keep running,” Fury said. “Fight Dubois at the Copper Box now.”