Eddie Hearn, who promotes IBF, IBO, WBA, WBO heavyweight world champion Anthony Joshua, says a unification with WBC champion Deontay Wilder needs to happen right now - because sooner than later the sanctioning bodies will begin ordering Joshua to make mandatory defenses.

While Hearn was attempting to make a Joshua-Wilder fight a few months ago, the WBA ordered the British boxer to face Alexander Povetkin in a mandatory defense.

And Povetkin was knocked out by Joshua in seven rounds in September, at Wembley Stadium in London.

Joshua is scheduled to return on April 13 at Wembley, and Wilder is the top target for the date.

But Wilder is targeting a rematch with unbeaten Tyson Fury. The two big men fought to a controversial twelve round split draw on December 1 at Staples Center in Los Angeles. 

If Wilder goes through with the Fury rematch, then Hearn fears that Joshua will be tied up with mandatories. Of course a unification could trump a mandatory obligation if the two sides ever reach an agreement. 

"Another reason why the undisputed title fight must happen now is because, sooner or later, we'll have different mandatory challengers," Hearn said to Sky Sports.

"And they might be fights that no one has an interest in. Wladimir Klitschko did that for years except he took the fights that no one had an interest in. Keep defending, keep defending - but you build a poor resume and AJ isn't interested in that. He wants the big fights."

If Wilder is removed from the running, then Dillian Whyte has a “very, very good” chance of being Joshua’s next challenger, according to Hearn.

“Dillian deserves a world title shot and he’s in his prime or approaching his prime, and that’s the time to fight. Him and ‘AJ’ is a brilliant fight," Hearn said.

“We haven’t got long (to make Joshua’s next fight). I’m sure we’ll be on the phone to Dillian within the next week. The priority is he wants to fight Wilder, but I don’t believe that will happen. If it’s an April 13 date at Wembley you’ll need it on sale at the end of January. He’s 80 percent likely to fight at Wembley on April 13."