Conor McGregor has told Floyd Mayweather to "say it to my face" after the boxing legend criticised the UFC champion.
McGregor became the first dual-weight champion in UFC history with a second-round knockout of Eddie Alvarez at Madison Square Garden last weekend.
However, Mayweather - one of the greatest boxers of all-time - wasn't impressed with comparisons between the two athletes, and branded them "disrespectful".
In comments relayed by The Mirror, Mayweather said:
"If you say he's the Floyd Mayweather of MMA, then I'm trying to find out. Has he ever made $300million in one night? $100m in one night? $70m in one night?"
"Conor McGregor can go out there and do what he do, but never compare Conor McGregor to me, it's a total disrespect.
"Once again, I'm an elephant. Elephants don't beef with ants, an elephant is so large it doesn't even see ants."
Mayweather doesn't seem keen on the idea of a huge cross-code battle with McGregor, despite the two having a long-standing feud that has included an exchange of words on more than one occasion.
McGregor, who is still in New York celebrating his momentous victory, spoke to TMZ about Mayweather's comments.
He said: "Do you believe him?
"Tell him to say it to my face."
The lack of respect between the two would make for an incredible battle if they were ever to fight, with the Irishman far more in tune to the idea than the American.
UFC boss Dana White has been quick to defend his prized asset, and labelled Floyd Mayweather as one of the most boring fighters in history.
White stated: "Conor McGregor, if he touches you, you go to sleep. Floyd puts people to sleep too, with his fighting style, not with his hands.
"Floyd can say what he wants about Conor, but even other fighters have to respect him. He's special. Floyd's never even come close to doing to other fighters what Conor does."
Mayweather is yet to respond to the words of McGregor and White.