Deontay Wilder demanded a rematch with Tyson Fury, calling for the WBC champion to honour his agreement for a blockbuster trilogy showdown.
A third Wilder-Fury clash has been touted after the latter stripped the American of the WBC title in February's rematch at the MGM Grand in Las Vegas following a draw in the first fight in 2018.
Wilder (41-1-1) has the right to a third bout against British star Fury (30-0-1) but, although December 19 was suggested as a possible date, nothing has been finalised amid the coronavirus pandemic.
Fury announced in October that he had ended his interest in another rematch, while Wilder's co-manager denied claims his fighter no longer had a contractual clause for the bout, which would leave the former free to face Anthony Joshua instead.
A deal for two 2021 fights between Fury and Joshua, who regained the WBA, IBF, WBO and IBO heavyweight world titles by beating Andy Ruiz in a rematch last December, was agreed in principle in June.
Wilder called out Fury via social media on Saturday, writing on Twitter: "Fury Be A Man. @Tyson_Fury it is time for you to be a man and honour your agreement. What is this bull**** of you fighting Carlos Takam instead of me, you got to be kidding…
"When that fight was a draw, I told you that I would give you a rematch. You know I was offered more money to fight Joshua than I was getting to fight you. Again being a man of my word, I fought you like I said I would…
"In the rematch agreement, there was a rematch clause. Now it is time for you to be a man and honour your word, instead of trying to weasel out of our agreement. Scared people run by a scary man will break his contract you coward Azz b****!"
Fury produced a seven-round demolition via TKO against Wilder, who suffered his first loss.
In the accompanying video, Wilder added: "I saw in the first fight when Ricky Hatton was pulling down your gloves to put your fists in the improper position. Y'all tried the same method the second time, but this time, you scratched flesh out of my ears which caused my ears to bleed.
"It's impossible for a brand-new 10-ounce glove to bend, to keep a smushed-in form or to have loose space. I highly believe you put something hard in your glove. Something the size and the shape of an egg weight.
"It's the reason the side of my face swelled up in the egg weight form and it left a dent in my face as well.
"But in the midst of all, you still couldn't keep this king down. You would have had to kill me. In the end, it took a crap-in-a-bucket referee and a disloyal trainer to throw the towel in just to stop me."