Wilder now holds the WBC title, with Joshua holding the WBA, IBF and WBO titles, and the fight will see the victor taking all of it home.
Wilder's manager Shelly Finkel revealed a rematch clause was part of the original offer from Hearn.
There is a lot of sorting out to do for this fight, but great news that in principle he seems to be on board for the idea of coming to the United Kingdom for the fight. Deas says Joshua turned down a $50 million offer to fight in the United States and that both fighters will make less than they would have to fight in Joshua's home country.
"I spoke to AJ and Rob McCracken this morning and obviously we saw Deontay Wilder's stuff on social media".
So the heavyweight division appears to be getting its biggest fight.
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"The fact that we've lost four weeks waiting for an answer from Deontay Wilder makes a fight happening in 11 or 12 weeks of this magnitude unlikely", Hearn said. We've got to speak to them about what date suits them.
"It's obviously the fight we want".
"We're going to dealing with that and making sure he gets the relevant paperwork".
Joshua-Wilder would likely sell out Wembley Stadium again.
Another possible outlet is the Perform Group's DAZN sports streaming service, which is due to launch in the US later this summer, with Hearn's recently agreed to eight-year, $1 billion deal to provide boxing content due to begin in September. "It's up to them to choose".
The victor of the first fight will become the undisputed heavyweight champion. A Joshua-Wilder fight on the service would raise its now nonexistent American profile, but it would also limit the US revenue for the bout. Wilder (40-0, 39 KOs), 32, of Tuscaloosa, Alabama, won his belt in 2015 and has made seven title defenses, including scoring a massive 10th-round knockout of then-unbeaten top contender Luis "King Kong" Ortiz in a riveting fight on March 3 at Barclays Center in Brooklyn, New York.