The WBO ordered Joshua to step into the ring against with former undisputed cruiserweight champion Usyk as a proposed all-British heavyweight battle with Tyson Fury fell through.
IBF, WBA and WBO champion, Joshua was due to take on Fury in Saudi Arabia in August before a court arbitration in the United States ruled the WBC strap-holder must face Deontay Wilder for a third time.
With Fury and Wilder III set to be staged in Las Vegas on July 24, Joshua (24-1) will come up against Ukrainian Usyk (18-0) two months later.
Joshua’s promoter, Hearn did not reveal a venue for the bout, but revealed during an Instagram live chat: “Working towards September 18 or September 25.”
The Matchroom boss added: “Joshua-Usyk announcement? Don’t want to say two weeks, because you guys are bored of me, saying that, but soon – September 25 is the date.”
Joshua, this week, vowed a showdown with Fury is still on the cards.
“Unfortunately, his [Fury’s] team let the whole boxing world down,” Joshua told Sky Sports. “I will still be here, still ready to put on a show.
“[The Fury fight can happen at the] end of the year. Let me get past Usyk first. But with or without Usyk in my life, I will fight Fury.
“Usyk isn’t the be-all and end-all. Usyk doesn’t determine the Fury fight. The Fury fight has to happen. It’s a big fight, bigger than boxing, bigger than the belts.
“It will happen. After the Usyk fight, after I will defend my belts. The fight will be bigger, better than what it would have been.”
