However, both camps are confident of settling the issue swiftly.
The win marks Holly Holm's first victory in 19 months since defeating Rousey.
Robert Whittaker takes on Yoel Romero, with the winner guaranteed to face Michael Bisping.
McGregor first floated the idea of challenging Mayweather nearly two years ago.
'The Money Fight' will bring sanitised sports events to a new low as both entities' struggles are exposed.
UFC heavyweight champion Stipe Miocic has called out his boxing counterpart on Twitter.
The highly anticipated boxing match will take place in Las Vegas on 26 August.
The bout will be a 12-round fight with 10-ounce gloves and at a weight limit of 154 pounds.
Max Holloway comprehensively defeated Jose Aldo via TKO in the third round.
Mayweather Promotions were due to formally request the date from the Nevada State Athletic Commission.
Chael Sonnen says Ronda Rousey only understands one thing which is aggression.
The duo are looking to have their boxing fight take place in August.
Thompson had previously revealed that he would like to avoid fighting St-Pierre.
Reports from the Los Angeles Times had suggested that UFC president was not involved in current negotiations.
UFC president Dana White not involved in talks over cross-code clash.
Tate: 'I feel like I was blessed to have a rival like Ronda Rousey.'
In the last year, the UFC lightweight champion earned $34m (£26m).
The UFC heavyweight champion had previously spoken of his interest in a boxing fight with Joshua.
Holloway is only the second UFC champion from Hawaii after the legendary BJ Penn.
Shevchenko: "Ronda has good takedowns and submissions, but she needs to work on her distance [to throw punches]."
But former world champion boxer hopes UFC superstar can "splatter" Mayweather.
Rogan believes McGregor can be considered the best featherweight even if he never fights again.