Floyd Mayweather has offered UFC champion Conor McGregor $US15 million ($A20m) and a percentage of pay-per-view sales for a crossover boxing bout.
Mayweather, who retired in September 2015 after accumulating a 49-0 record, told ESPN he would require a guaranteed $US100 million ($A134m) to make the fight happen.
"I'm a businessman and it makes business sense," the 39-year-old American said.
"Bring him over to the boxing world, and I'll show him what it's like."
Irishman McGregor, the reigning lightweight and former featherweight UFC champion, has been challenging Mayweather to a fight for months.
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The biggest pay-per-view draw in mixed martial arts, McGregor is contracted to UFC and the organisation would have to approve any fight.
Mayweather, who won world titles in five weight divisions and took home earnings in excess of $US800 million ($A1.1 billion) over his 19-year boxing career, said initial talks had taken place.
"We tried to make the Conor McGregor fight," he added.
"They know what my number is. My number is a guaranteed 100 million. That was my number.
"We are willing to give him 15 million and then we can talk about splitting the percentage, the back end, on the pay-per-view."
