LONDON - Floyd Mayweather has declared himself "out of retirement" to fight Conor McGregor, and demanded the Irish mixed martial arts champion commit to a crossover bout in June.

"I'm not ducking or dodging anyone," Mayweather said in London on the weekend.

"I'm only coming out of retirement for one person, and that's Conor McGregor.

"We don't need to waste no time. We need to make this happen quickly. Let's get it on in June."

For months, McGregor has been challenging Mayweather, an undefeated five-division world boxing champion who retired in 2015 with a 49-0 record.

The two sides have yet to reach terms and have a number of major hurdles to overcome.

Mayweather has asked for a guaranteed $100 million to make the fight happen, with $15 million going to McGregor, while UFC president Dana White has talked of $25 million to each fighter, plus pay-per-view money.

McGregor, the biggest pay-per-view draw in mixed martial arts, is contracted to UFC and the organization would have to approve the fight.

McGregor became UFC's first simultaneous two-weight champ in November when he beat Eddie Alvarez for the lightweight belt.

The pair will also have to agree to a format - which Mayweather insisted would be straight boxing.

"We cannot mix up the rules and regulations because I'm the A side," he said.

"He called me out. You call me out, we have to go by my rules. If I called him out then we'd have to go by his rules.

"It's always boxing."

The pair have done their part to drum up interest, exchanging a number of verbal barbs at public appearances.

Mayweather reiterated his claim that McGregor was all talk and no action.

"Conor McGregor, stop ducking and diving. Tell the UFC to let's make this fight happen," he said.

The former pound-for-pound king also took a shot at the sport of mixed martial arts, explaining why any fight with McGregor needs to be a boxing match.

"Real men fight standing up," Mayweather said in an interview with Fighthype.com.

"I'm from the old school. I'm not gonna kick my shoes off. I'm not gonna be between no man's legs, wrestling on the ground. I'm gonna stand up and kick his butt."

Agencies