Floyd Mayweather was talking trash at Conor McGregor on Tuesday and the UFC champ couldn’t respond. Well, at least not in a way everyone in attendance at the Mayweather vs. McGregor World Tour press conference at Staples Center in Los Angeles could hear it.

McGregor’s microphone suddenly stopped working for reasons unknown, forcing the Irishman to yell at “Money May” the old fashioned way.

McGregor blamed Showtime and Team Mayweather for the malfunction at his own separate presser later in the day.

“They can do nothing after Aug. 26,” McGregor told reporters. They can try to do all these little tricks all they want. Aug. 26 this man will be unconscious. He’s too small. He’s too frail. That’s it, what more can I say?”

More than 11,000 fans crowded into Los Angeles's Staples Center for a raucous first live showdown between former boxing world champion Mayweather and Irishman McGregor, one of the biggest stars of mixed martial arts.

The two men are set to face each other in Las Vegas on August 26 in what could be the richest fight in history after finally agreeing to climb into a boxing ring following a year-long guessing game over whether they would ever do battle.

Tuesday's fiery face-off saw the swaggering, cocksure McGregor strut onto stage confidently in a three-piece suit featuring pinstripes made up of an offensive two-word insult.

The immaculately tailored profanity set the tone for a spectacle shot through with an endless torrent of abuse from both fighters, no doubt delighting promoters as they drum up hype for a bout which will demand $10,000 for ringside seats.

McGregor, who will start as an overwhelming underdog against one of the most accomplished defensive fighters in history, was bullish about his prospects of victory. "The 0 has got to go," McGregor declared, referring to Mayweather's perfect 49-0 record.