WBC heavyweight champion Deontay Wilder says he has agreed a rematch against Luis Ortiz.
The news comes despite Anthony Joshua, the IBF, WBO and WBA 'super' heavyweight champion, saying he wanted face-to-face talks with Wilder to ensure a fight is agreed this year.
However, Wilder appears to have other plans, tweeting on Wednesday morning: "To all my fans, I want to announce that Luis Ortiz and I have signed for a rematch, with the date and site to be announced shortly. All my controversial fights must get dealt with ASAP."
Wilder beat Ortiz in their first fight in New York last year, knocking out the Cuban in the 10th round to inflict his only professional defeat.
The American's most recent fight was a first-round destruction of Dominic Breazeale to record the ninth-straight defence of his WBC title.
Joshua fights Andy Ruiz Jr on Saturday, live on Sky Sports Box Office, and his promoter Eddie Hearn had urged him to concentrate on impressing on his US debut before calling out Wilder.
He said: "Do we have to make the Wilder fight? More than anything. Biggest fight in world boxing and one of the biggest heavyweight fights of all time.
"I'm scared of Ruiz Jr and especially of Wilder - he can punch! But don't you want those moments, a chance to be undisputed?
"You think we don't want it? We want it so badly. AJ needs to say: 'Now! November or December, no excuses, let's do it'."
Watch Anthony Joshua vs Andy Ruiz Jr on Saturday, live on Sky Sports Box Office, from 10pm. Book it via your Sky remote or book it online here. Even if you aren't a Sky TV subscriber you can book and watch it here.