Tyson Fury's potential heavyweight unification bout with Oleksandr Usyk could be in doubt after the Gypsy King turned down a 60-40 purse split, according to the Ukrainian's promoter Alex Krassyuk.

The duo's teams are in discussions for an undisputed clash, and negotiations seemed to be nearing a conclusion earlier this week.

Fury's promoter Frank Warren revealed both camps were looking to set a date and venue for the bout, while Usyk himself said both men "need this fight".

But Krassyuk has now claimed Fury's camp have turned down an increased offer for a 60-40 split favouring the fight's winner, having also reportedly pushed against an even 50-50 purse.

"Frank Warren said he's got a pot and he needs to get the agreement of both parties to participate," Krassyuk told talkSPORT.

"If the money in the pot is not enough, it won't happen. I completely agree with it. On our side, I have nothing more to add.

"We have said that we want this fight to happen as much as possible, and we are in the position to share whatever the fight generates.

"But boxing is a sport of two men and if only Usyk gets into the ring, there won't be a match for undisputed. It will be shadowboxing of the unified champion.

"We initially agreed for 50-50. But then Tyson was asking for some bigger money. We made it clear that we are ready to go 60-40, but the winner takes 60.

"That was our latest offer [but Fury turned it down], exactly."

Warren previously indicated there would be no negotiations beyond the end of this week, with both parties reportedly eyeing up an April 29 bout at Wembley Stadium.

"We're still none the wiser, we're still waiting for it to be done," Warren said. "It's all coming to a head now, but it's still not done.

"You need the agreement of both boxers to make it happen and at the moment we haven't got that, so that's where we're at.

"We're working hard to make it happen. But I would say it's not going to go past the end of this week because the proposed date is April 29."