McGregor v Mayweather: Conor McGregor vows to knock Floyd Mayweather out inside four rounds

McGregor has never boxed as an amateur or professionally but will face undefeated former multiple world champion Mayweather at the T-Mobile Arena on August 26 under normal boxing rules.

However, the 28-year-old Irishman is confident he can achieve something which proved beyond the likes of Manny Pacquiao, Saul Alvarez and Oscar de la Hoya and beat the American.

Speaking in Los Angeles at the first stop of a four-city media tour which will also take in Toronto, New York and London over the coming days, McGregor said on a Showtime live stream: "I am honoured to be here, to give you this spectacle. 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.

"I am just up here embracing everything. No-one can do anything to me. I am just enjoying myself and having a good time.

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

"All these rules, all these restrictions, it doesn't faze me; it amuses me. It is funny to me all these rules.

"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 100million US dollars at one stage - reportedly his fee for coming out of retirement - hit back before an expletive-laden exchange between the pair.

Mayweather told the 20,000-strong crowd: "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.

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

McGregor retorted: "You haven't knocked anyone out in about 20 years."

Mayweather added: "We talking about from the nineties to now, world champion 18 years, but it is no problem. 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. Which was do you want to go? All you need to do is show up and I will do the rest.

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