Anthony Joshua has urged Deontay Wilder not to "rob the fans" but agree to an undisputed world heavyweight title fight.
Joshua wants to face his fellow champion in a battle for every major belt if he comes through Saturday night's defence of the IBF, WBA and WBO gold against Andy Ruiz Jr.
He has now appealed to WBC titleholder Wilder to reverse his decision to fight Luis Ortiz next.
Joshua told a press conference on Thursday: "Whatever he is doing with his career, good luck to him. However, I am a fan of the sport. I have tried to challenge all the best fighters out there, bar one or two. I am reaching out to them.
"Let's not rob the fans of a good fight. I am a fan of this sport and I feel like I'm robbing myself of a good fight.
"Good luck to whatever he is doing. But if he wants to come and see us - because he hasn't announced a date or a venue - then we can have a conversation."
Joshua and Wilder are unbeaten in a combined 64 fights, 62 of which have been won by knockouts.