UFC star Conor McGregor says he’ll out boxing great Floyd Mayweather within four rounds when the pair does battle in their super-hyped bout next month.

Speaking in Los Angeles in the first of a series of four press conferences in three countries to spruik the fight, Irishman McGregor said he was confident of achieving something the likes of Manny Pacquiao, Saul Alvarez and Oscar de la Hoya have failed to do.

“I am honoured to be here, to give you this spectacle,” McGregor said.

“His little legs, his little core, his little head, I am going to knock him out inside four rounds, mark my words.

“I am a young, confident, happy man that has worked extremely hard for this.

“He will be unconsciousness in four rounds. He has never faced this. I don’t fear him.

“All I need is a gum shield. Line me up to the ring and I am good to go.”

Mayweather, who brandished a cheque for $US100million [$A130 million] at one stage – reportedly his fee for coming out of retirement –hit back before an expletive-laden exchange

“I don’t care if it’s a ring or it’s an octagon, I will kick ass. I don’t back down for anybody,” Mayweather told the 20,000-strong crowd.

“You line them up and I will knock them down. On August 26, I’m gonna knock this b**** out too.”

Watch part of the press conference (warning: explicit language)

https://www.youtube.com/watch?v=BbVeL5PiSHs

McGregor, who won world titles in two UFC weight divisions, was quick with his retort.

“You haven’t knocked anyone out in about 20 years,” he said.
Mayweather has a 49-0 record but his last knockout was almost six years.

“We talking about from the nineties to now, world champion 18 years, but it is no problem,” 40-year-old Mayweather said.

“I’m not the same fighter as I was years ago, but I got enough to beat you.

“You will wave that white flag. You are going out on your face or your back.

“God only made one thing perfect, and that is my boxing record.”