UFC lightweight champion McGregor, 28, earlier said he had concluded his side of the negotiation process and that he hoped Mayweather would sign to fight “in the coming days”.
McGregor last year obtained a boxing licence granted by the California State Athletic Commission, which would allow him to box in the US state, as part of his pursuit of a cross-sport showdown with Mayweather.
America's Mayweather is accompanying his protege Gervonta Davis in London, where on Saturday he makes the first defence of his IBF super-featherweight title against Liam Walsh.
He was asked about the latest development regarding a long-discussed fight with McGregor, but responded: “This is Liam Walsh and Gervonta Davis' press conference. Let's focus on these two competitors.
“That's total disrespect to both of these fighters, it's their press conference, let's talk about them. Both of these fighters deserve respect.”
A potential fight between the two highest-profile fighters from each code has been discussed for much of the past 12 months.
In a statement issued to TheMacLife.com, the Irishman said earlier on Thursday: “It is an honour to sign this record-breaking deal alongside my partners Zuffa LLC, the Ultimate Fighting Championship and Paradigm Sports Management.
“The first, and most important, part of this historic contract has now officially been signed off on. Congratulations to all parties involved. We now await Al Haymon and his boxer's signature in the coming days.”
On Wednesday, the UFC president Dana White revealed on TNT's live NBA play-off game broadcast that negotiations with McGregor had been completed ahead of what would likely prove a popular fight.
“The McGregor side is done,” White told TNT. “I'm starting to work on the Mayweather side now.
“I'm not saying the fight will happen, but I've got one side done: now it's time to work on the other. If we can come to a deal with Haymon and Mayweather, the fight's going to happen.”
Mayweather, 40, last fought in September 2015 when he outpointed Andre Berto.
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