Former world boxing champion Floyd Mayweather says a fight with mixed martial arts star Khabib Nurmagomedov is “happening”.

Both Mayweather (50-0) and Nurmagomedov are (27-0) are unbeaten in their fighting careers, although the American said they would meet in the boxing ring. “He called me out, so you have to come to my world,” Mayweather told TMZ Sports on Wednesday. “I seen in an interview, he said when he hit Conor McGregor, he knocked Conor McGregor down. He said I didn’t knock him down. OK, Khabib. You got my leftovers. Whoop-dee-do.”

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Mayweather retired after his last fight, in which beat another UFC star, McGregor. However, the 41-year-old said he would be willing to return to the ring to take on Nurmagomedov. “We’re fighting,” Mayweather said. “I’m my own boss. I can’t say what’s going on on Khabib’s end, but on my end we can make it happen.”

Any fight would be incredibly lucrative for both men. “When I face Khabib, I’m getting a nine-figure payday,” Mayweather said. “Yes, more than the McGregor fight. Probably $100m more, guaranteed. It could be somewhere upwards of $110m to $200m guaranteed.”

The attraction for Nurmagomedov is clear. The Russian earned $2m from his fight with McGregor but that figure could swell to tens of millions for a showdown with Mayweather. He is also under a temporary suspension for his part in the chaotic scenes at the end of UFC 229. After he defeated McGregor earlier this month, Nurmagomedov leapt out of the octagon and began brawling with one of his opponent’s trainers. Members of his team also fought with McGregor.

Rumours of a fight between Nurmagomedov and Mayweather started on Sunday. In a video posted on Instagram by Mayweather CEO Leonard Ellerbe, Nurmagomedov said: “Let’s go Floyd. We have to fight now: 50-0 versus 27-0. We are two guys who never lose. [But] in the jungle there is only one king. Of course, I am the king because he cannot drop McGregor but I drop him easily. Let’s go.”

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Mayweather did not knock down McGregor during their fight last year, but appeared to be toying with his opponent in the early rounds. He has not fought since overcoming McGregor but stated last month that he was coming out of retirement for a rematch with Manny Pacquiao.