McGregor begins training for Mayweather: 'Sign your end Floyd or you are just a mouth'

Conor McGregor says he has started training for Mayweather and calls out the boxer on social media.

UFC lightweight champion Conor McGregor posted on Saturday that he had begun 'day one' of his training camp for a boxing megafight against Floyd Mayweather Jr.

The charismatic Irishman claims to have signed his part of the contract but is waiting on Mayweather to finalize the deal. UFC president Dana White is expected to meet with the boxing great in the coming days but McGregor is getting impatient, ordering 'Money' to complete the contract.

Despite claiming to have fulfilled his end of the bargain, 'The Notorious' is still not licensed to box in Nevada but reportedly submitted an application on Thursday.

McGregor, 28, is the fastest rising star in combat sports and became the UFC's first simultaneous two-division champ at UFC 205, capturing both the featherweight and lightweight world titles. The Dublin local has arguably the best hands in the sport, finishing almost all of his opponents via KO or TKO, but has never professionally competed in the boxing ring.

Mayweather, 40, is one of, if not, the greatest defensive boxer of all time and is undefeated with a professional record of 49-0, cruising to a unanimous decision in his last bout against Andre Berto.

McGregor vs. Mayweather has been slammed by hardcore fans but is likely to be the biggest fight in prize-fighting history, drawing mega attention from the casual boxing and MMA fans, as well as audiences that traditionally don't watch combat sports.

According to White, the original targeted date of September 16 has been pushed back due to the announcement of Gennady Golovkin vs. Canelo Alvarez.