Anthony Joshua promised to knock Jarrell Miller out as the pair clashed at a heated news conference at Madison Square Garden on Tuesday.
WBA, WBO and IBF heavyweight champion Joshua will make his United States debut against Miller in New York City on June 1 and sparks were flying from the off at a media event.
Miller shoved Joshua hard in the chest within seconds of taking to the stage, before security intervened on multiple occasions as promoter Eddie Hearn ushered the British fighter away.
The confrontation prompted a change of format for the news conference, with Hearn encouraging the two athletes to stay in their seats rather than approach the podium.
"I'll sit down when I feel like it," Miller responded.
"I'm home," he then shouted, banging the desk in front of him. "[Joshua] is not from these streets, and he's going to come here and tell me I'm the underdog?"
Anthony Joshua through the years
Anthony Joshua through the years
Great Britain's Anthony Joshua poses with former gold medalist Lennox Lewis as he celebrates his Gold medal following his Super Heavy Weight Final against Italy's Roberto Cammarelle on day sixteen of the Olympic Games at the ExCeL, London.
Great Britain's Anthony Joshua (left) celebrates his win against Italy's Roberto Cammarelle in the Men's Boxing Super Heavy (+91kg) Final at the ExCeL Arena, on the final day of the London 2012 Olympics.
Great Britain's Anthony Joshua celebrates with his Gold medal following his Super Heavy Weight Final against Italy's Roberto Cammarelle on day sixteen of the Olympic Games at the ExCeL, London.
Anthony Joshua during a media workout at The English Institute of Sport, Sheffield
British boxer Anthony Joshua celebrates beating US boxer Charles Martin (not pictured) following their IBF World Heavyweight title boxing match at the O2 arena in London on April 9, 2016
Britain's Anthony Joshua won the IBF world heavyweight title with a sensational second round knockout of outclassed American rival Charles Martin. Olympic champion Joshua, 26, had Martin on the canvas twice in the second round to record his 16th knockout in all 16 professional fights he has contested. Joshua becomes the sixth British fighter to win a world heavyweight title. / AFP / JUSTIN TALLIS (Photo credit should read JUSTIN TALLIS/AFP/Getty Images)
CARDIFF, WALES - MARCH 31: Joseph Parker blocks a punch from Anthony Joshua during there WBA, IBF, WBO & IBO Heavyweight Championship title fight at Principality Stadium on March 31, 2018 in Cardiff, Wales. (Photo by Richard Heathcote/Getty Images)
Britain's Anthony Joshua (L) throws a punch at Cameroon-born Carlos Takam during their world Heavyweight title fight at The Principality Stadium in Cardiff on October 28, 2017. / AFP PHOTO / ADRIAN DENNIS (Photo credit should read ADRIAN DENNIS/AFP/Getty Images)
London , United Kingdom - 29 April 2017, Anthony Joshua, right, exchanges punches with Wladimir Klitschko during their Heavyweight Championship contest for the IBF, IBO Heavyweight and WBA Super Heavyweight Championships of the World at Wembley Stadium, in London, England. (Photo By Brendan Moran/Sportsfile via Getty Images)
Britain's Anthony Joshua (R) throws a punch at Ukraine's Wladimir Klitschko during the ninth round of their IBF, IBO and WBA, world Heavyweight title fight at Wembley Stadium in north west London on April 29, 2017. / AFP PHOTO / Ben STANSALL (Photo credit should read BEN STANSALL/AFP/Getty Images)
LONDON, ENGLAND - JUNE 25: Anthony Joshua of Great Britain lands a punch on Dominic Breazeale of The USA during their IBF World Heavyweight Championship bout at The O2 Arena on June 25, 2016 in London, England. (Photo by Richard Heathcote/Getty Images)
Anthony Joshua celebrates defeating Alexander Povetkin by Knockout at Wembley Stadium, London.
Anthony Joshua celebrates with his father Robert Joshua after victory over Joseph Parker in their WBA, IBF, WBO and IBO Heavyweight Championship contest at the Principality Stadium, Cardiff.
Anthony Joshua celebrates victory over Carlos Takam during the IBF World Heavyweight Title, IBO World Heavyweight Title and WBA Super World Heavyweight Title bout at the Principality Stadium, Cardiff.
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Hearn described the start of the event as "a little bit spicy" and the heat rose again as the pair took the microphones.
Miller said: "I'm ready. You have no idea. I breathe, eat, sleep Anthony Joshua.
"I've got a picture of him as my screensaver. Anthony Joshua. I've got a picture on my wall. Anthony Joshua. I wake up in the morning and think: Anthony Joshua."
The American then repeatedly interrupted Joshua as the two traded jokes and insults, leading the Briton to ask: "How old are you?"
He added: "Miller's a little b****. I'm going to knock him the f*** out on June 1. There's no doubt about that."
Joshua extended the event even after Miller departed the stage, telling reporters of the deal behind the fight: "I just gave him a big pay cheque, some cheeseburgers, and he was ready, he was there.
"He has no brain, so it's not hard to get inside his head. It was an easy negotiation."