Conor McGregor offered $15m by Floyd Mayweather for crossover bout

Conor McGregor has previously tweeted this mocked-up picture of the two men

Five-weight boxing world champion Floyd Mayweather has offered the UFC champion Conor McGregor $15m (£12.2m) to face him in the ring.

Mayweather retired unbeaten in 2015 but told ESPN a bout with Irishman McGregor - who has a boxing licence - was the only thing that could tempt him back.

"I'm a businessman and it makes business sense," the 39-year-old American said.

McGregor, 28, has previously said he wants $100m (£80m) to fight Mayweather.

Mayweather, who retired from boxing with a perfect 49-0 record after defeating Andre Berto in September 2015, said initial talks with McGregor's representatives had taken place.

"We tried to make the Conor McGregor fight," Mayweather said. "They know what my number is. My number is a guaranteed $100m. That was my number.

"We are willing to give him $15m and then we can talk about splitting the percentage - the back end - on the pay-per-view."

McGregor became the UFC's first dual-division champion in November and has previously challenged Mayweather to a fight under mixed martial arts rules.

His boxing licence has been granted by the California State Athletic Commission, allowing him to box in the US state.

However, he is under contract with the UFC and any potential fight against Mayweather would have to involve a co-promotion or the UFC's blessing.

Conor McGregor posted this cartoon on his personal Twitter feed on Wednesday, after Mayweather's interview with ESPN had aired