Britain's world heavyweight champion, 31, had initially been set to defend his IBF, WBA, WBO and IBO titles against WBC champion Fury on August 14 in Saudi Arabia, but that was derailed when the latter was ordered to face Deontay Wilder.
Instead, Joshua's next fight on September 25 will be in his home city of London, England. He will face Usyk, the former unified cruiserweight champion, who outpointed long-time contender Dereck Chisora to win the WBO Inter-Continental title last year.
Usyk, 34, has not lost after 18 professional fights. And the British boxer believes the Ukrainian will bring the heat when they battle for three of the four major world titles.
When asked why talks had broken down between the two sides, Joshua replied via Sky Sports: "I don't want to point any fingers. I was definitely ready. We move forward.
"I've got another challenger who's good, just as good. I have to be serious about him now.
"He will definitely step up, he will definitely take the fight. That's what I need - people that are serious.
"I would have loved to have boxed for the undisputed championship because it was a big fight for the public. We had everything set up.
"I have to move forward and not keep dwelling."
He has also spent a considerable amount of time training with fellow Ukrainian superstar Vasyl Lomachenko.
Olympic gold medallist Joshua added: "The most important fight for me is the next one but you have to have a vision of where you want to get to. I have to stay consistent and stay ready.
"Once I fight Usyk, who knows what will happen next?
"I have to stay on track and ready for each fight, but have a long-term plan.
"It's about the belts, not the person. I don't mind who it is. I want to fight for legacy."
Speaking on the DAZN Boxing Show, Joshua's promoter Eddie Hearn confirmed on Tuesday night that a full crowd of 60,000 fans will be able to attend the Tottenham Hotspur Stadium in White Hart Lane, London on September 25.
“All the seats will be open,” he said. “So yesterday in the UK, we had something called Freedom Day, which basically meant life returns as we used to know it, hopefully.
“So everything now is officially open. So we will be having over 60,000 there on September 25, for Joshua against Usyk, which will be fantastic. I've definitely aged over the last three months because of all the questions, you know, ‘What's happening with this Joshua-Fury?'
“Because there was no tearing rush, and we wanted to get everything right, particularly with the announcement of Freedom Day. Yesterday, we just took our time.
“Today's a nice day where we can just get everything out and say, guys, I know that the world wanted Joshua against Fury, but, I tell you, you got a great fight.”News Now - Sport News