Tyson Fury and Deontay Wilder had to be separated as they came face-to-face during a fiery news conference in London Monday.
Undefeated former heavyweight world champion Fury (27-0, 19 KOs) faces WBC titlist Wilder (40-0, 39 KOs) on Dec. 1 in Los Angeles and the pair clashed after Fury challenged his opponent to a pre-fight spar.
"Can we have a spar now?" Fury said after questioning Wilder's punch-power. "Let me feel this power. Come on, get up."
The fighters then squared up, with Fury's promoter Frank Warren forcing himself between the pair.
But Fury continued to challenge Wilder, encouraging the American to punch him. Wilder then pushed Fury in the chest before they were separated by security.
"If I hit you now I can't show you on Dec. 1," Wilder said after the scuffle.
Monday's press conference kicked off a media tour which will see the fighters appear in New York on Tuesday and L.A. on Wednesday.
The fight was agreed following Fury's win over Francesco Pianeta in Belfast in August, with Wilder appearing ringside. The men had already exchanged insults after Wilder crashed Fury's weigh-in ahead of the fight.
During the press conference Fury also took exception to being introduced as Wilder's challenger by host Paul Dempsey.
"Just a little correction for you, I am no challenger to no man," Fury said as he was introduced to the stage. "I am the lineal heavyweight champion of the world. That means I am the best of the best, the elite champion. This fight is two champions colliding."
Fury beat Wladimir Klitschko in November 2015 to become the WBA, WBO and IBF world champion but didn't fight again for two-and-a-half years due to a number of personal issues.
He made his comeback against Sefer Seferi in June before beating Pianeta in only his second fight since his return.