Anthony Joshua
Anthony Joshua plans on fighting in September next. Pictured, Joshua poses with his belts after his WBA, IBF, WBO & IBO Heavyweight Championship title fight at Joseph Parker Principality Stadium in Cardiff, Wales, March 31, 2018. Richard Heathcote/Getty Images

Anthony Joshua's promoter Eddie Hearn has warned Deontay Wilder to accept their offer for a title unification fight or risk waiting even longer.

Joshua was seen last in action on March 31 against Joseph Parker as a unanimous decision win over the New Zealander saw him become a holder of the the World Boxing Organization, World Boxing Association, International Boxing Federation and International Boxing Organization heavyweight titles.

And with World Boxing Council heavyweight champion Wilder successfully defending his strap against Luis Ortiz earlier that month, the next plan in motion seemed to be a title unification clash between the unbeaten duo in which the winner would be the undisputed champion of the heavyweight division.

In early April, Joshua's team offered the American a flat fee of £8.8 million ($12.5 million) to fight in the United Kingdom with a 50/50 purse split rematch taking place in America soon after.

Wilder responded with a $50 million counter-offer as well as 50 percent of the event revenue so that Joshua would fight him before the end of the year, though Hearn would call the offer a PR move.

Since the pair of offers, there has been very little movement in finalizing the fight but Hearn claims they have been waiting on a response to their latest offer as his father Barry is currently in New York to meet up with Wilder's co-manager Shelly Finkel to see if a deal can be struck.

But while Joshua wants a fight with Wilder, he also wants it to happen in September and if there are any more delays, the Briton could end up fighting his World Boxing Association mandatory in Alexander Povetkin in a match that was already virtually agreed on, according to Hearn.

"I don't like making deadlines because sometimes it gets people's backs up but at some stage soon we have to make a decision," Hearn said, via Sky Sports. "We are close to closing a deal with Povetkin with (Andrey) Robinsky and World of Boxing and once the deal is closed, there is no Deontay Wilder."

"Wilder has had the latest offer from us for the last two weeks which was our improved offer and we are still talking to them and in fact, my dad is out in New York at the moment, and he might meet Shelly today. They have our offer so they have to accept it or move on. It's not a case of if you don't accept this offer the fight is dead, we will just fight Povetkin and carry on our negotiations to the next one."

"It has to be the next one, or the one after that. Joshua wants to fight. We've got an opportunity to go in September and Josh is keen to fight in that month and if Wilder wants it, it's there. But I do still believe Wilder will take this offer."

Povetkin notably fought on the same card as Joshua vs. Parker as he knocked out England's David Price in the fifth round for his 34th professional win.

With just one loss on his record, Hearn spoke of how the Russian is as tough a fight for Joshua as Wilder is.

"It is a very, very difficult fight, the Povetkin fight. He's lost once, to Wladimir Klitschko who did everything he could to try and stop him but couldn't do it," Hearn added. "He is an extremely tough man with extremely powerful people behind him and the entire nation behind him who will desperate to beat Anthony Joshua for a world heavyweight title.

"This is a serious fight and in many ways, it's as tough as the Wilder fight. Josh is up for all these fights, all these tests and he is certainly up for fighting Wilder. At the end of the day, Josh could lose to Povetkin and then the Wilder fight is up in smoke."