The ball is now in Anthony Joshua’s court.

Deontay Wilder, along with promoter Lou DiBella and manager Shelly Finkel, delivered a sizable offer to Joshua and promoter Eddie Hearn on Wednesday in hopes of finally completing a deal to crown a new undisputed heavyweight champion.

Wilder sent an email to both Hearn and Joshua’s manager, Robert McCracken, offering his fellow heavyweight titleholder a 50% split of the revenue against a $50 million guarantee for the proposed clash, which would take place between September and the end of the year, DiBella told THE RING.

Under the terms of the proposed deal, Wilder’s side would control aspects of the promotion, such as the site and network that would distribute the pay-per-view. Joshua would earn either $50 million or half of the revenue, whichever is greater. The deal also stipulates that the fight take place next with no interim bouts in between.

The counteroffer comes weeks after Hearn offered Wilder just $12.5 million to meet Joshua with all four heavyweight titles on the line.

“If Anthony Joshua is serious about wanting this fight next and Eddie is not stopping the fight from happening, they have a great offer to accept, especially given Eddie’s characterization of the size of the fight,” said DiBella. “To quote my friends across the pond who make this statement way too often, this is a massive fight.

“When you’re talking about these kind of numbers, you want great lead time, you want to be out there promoting this with adequate window to do that. This is biggest heavyweight fight in a generation.”

One caveat: Wilder insisted that the offer be accepted by Thursday. Hearn scoffed at that notion during an interview with THE RING. The email also stated that Wilder would total control and ownership of the show, per Hearn.

The guarantee is also another question mark. Typically in these instances, the money would be placed in escrow, securing the deal. Hearn said if he was making the offer, $50 million would be placed in escrow within 24 hours.

“I think it’s a wonderful PR move,” Hearn said, “but we still want to explore whether there’s any substance behind it so if can receive some formal paperwork, meaning contracts, proof of funds, where the money’s coming from and where the fight will take place, then we’ll consider it.”

The British promoter, currently in New York to promote Daniel Jacobs’ HBO fight on Saturday against Maciej Sulecki, said he has a meeting scheduled Friday with Finkle and Wilder’s adviser, Al Haymon. At the top of the agenda will be exploring “more realistic ways to make the fight.”

Even though Hearn isn’t positive whether the offer is “real or not,” he believes this is genuine progress toward an eventual deal for what’s surely the biggest fight that could be consummated in boxing.

“This could be the start of the fight opening up. … It’s going to start a conversation,” Hearn said. “We want to do this fight in the U.K., we’ve worked very hard on Anthony Joshua’s fights in the U.K., but if there’s a substantial offer for Vegas or New York,” we’d consider it.

“Anthony Joshua is not in a position where he wants financial risk,” Hearn stated.

Hearn estimated the fight could generate, conservatively, $40 million in the U.K., with $60 million also possible. In the U.S., where the pay-per-view market is far more robust, Hearn believes the bout could pull in 60 or 70 million with 600,000 to 700,000 buys in North America.

So either way, $50 million guaranteed is an extraordinary offer. At this point, the question isn’t whether the offer is real, or if the money is secured.

The conversation has now begun in a meaningful way, and it’s up to both sides to hammer out a deal to bring the two heavyweights together for a truly mega fight. An event that would feature two fearsome, undefeated punchers in the first massive heavyweight title fight since Lennox Lewis destroyed a shopworn Mike Tyson in 2002.

Mike Coppinger is the Senior Writer for RingTV.com. Follow him on Twitter: @MikeCoppinger