Anthony Joshua and Eddie Hearn
Anthony Joshua and Eddie Hearn are 'definitely' interested in a title unification fight with Deontay Wilder. Pictured: Anthony Joshua celebrates with the belts and promoter Eddie Hearn after winning the fight against Joseph Parker at Principality Stadium, Cardiff, Britain, March 31, 2018. Reuters/Andrew Couldridge

Matchroom Boxing promoter Eddie Hearn is happy that Deontay Wilder sent Anthony Joshua a lucrative fight offer but needs to see a real contract first.

Joshua is targeting every single belt in the heavyweight division as his unanimous decision win over Joseph Parker on March 31 sees him now hold the World Boxing Organization (WBO), World Boxing Association (WBA), International Boxing Federation (IBF) and International Boxing Organization (IBO) heavyweight titles.

A title unification fight with World Boxing Council (WBC) champion Wilder seems imminent in what is certainly the biggest and most lucrative contest in boxing today. However, an agreement seems hard to come by.

Earlier this month, Joshua's team reportedly offered the American a flat fee of £8.8 million ($12.5 million) to accept a fight with him in the United Kingdom, meaning Wilder would miss out on a split of the event revenue but would be entitled to a guaranteed rematch with a 50/50 purse split in the United States.

However, the "Bronze Bomber" and his team responded via email Wednesday with a new $50 million counter-offer as well as 50 percent of the event revenue for the Briton to fight him before the end of the year.

"It's a giant number. But it's also a giant fight," Wilder's co-manager Shelly Finkel said, as per ESPN. "It has to be the next fight for each of them. No rematch clause, and it's for all the belts."

"We asked for them to send us an acceptance [by the end of Thursday]. Joshua [previously] asked for $50 million against 50 percent, and we gave it to them. They probably don't believe it's this big of an offer, but it's an unbelievable offer. I hope they accept. Deontay is thrilled and believes Joshua will take it," Finkel added.

However, Joshua's promoter Hearn believes it is simply a PR move as while he received an offer letter, he did not receive an actual contract with specific details such as where the fight would take place.

"We don’t how real it is," Hearn said, as quoted on BoxingScene. "Deontay Wilder’s sent the letter and said ‘you’ve got to sign the contract tomorrow and there’s a fight’. We haven’t had a contract yet. It’s a wonderful PR move but we’ll see."

"It’s very nice of Deontay to make that offer, we need to see how secure that is, we need to see a contract, we want to know where it is and quite a lot of other things as well. But we’re definitely interested to look at those numbers," Hearn added.

Wilder last fought in March when he knocked out former undefeated Cuban boxer Luis Ortiz in the 10th round of their Brooklyn, New York, clash in a contest many felt was his toughest opponent yet.

The American notably took home a career-high $2.1 million payday from that fight and looks set to smash that figure should a fight with Joshua ever come to fruition.