Fury's UK promoter has suggested that there is a long way to go before the bout between the two heavyweight world champions can be rubberstamped.
Warren told talkSPORT: "At the end of the day, I can’t force Usyk to fight, I can’t force Tyson to fight. That’s their choice. They’re the guys getting in the ring and at the end of the day we’re either going to make this happen or not.
"We’re still none the wiser, we’re still waiting for it to be done, 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."
Warren confirmed that April 29 is the working date for the bout and he is expecting some progress by the end of the week.
He said: "But I would say it’s not going to go past the end of this week that’s for sure because the proposed date is April 29.
We have to contract with a venue and so forth to make it happen."
Warren emphasised that he and his fellow promoters are working hard to get the fight over the line.
He said: "I’m hoping we get it done because no one wants to see this fight more than me.
"I promise you, because you know what, no one’s ever promoted the four belts. It’s never happened. It’d be the first time, it’d be a history-making thing. It’ll be great.
"I believe Tyson wins the fight and that’s his legacy. I want it. But I can’t force people into a situation unless they’re comfortable. And if they’re not comfortable they won’t be mentally right for the fight, and I won’t do that either."