Floyd Mayweather has called on Irish MMA star Conor McGregor to "stop blowing smoke up everybody's ass" and sign a contract to fight.
A mooted fight between the high-profile pair could be the richest in the sport's history.
Speaking to ESPN's Ben Dirs, the undefeated boxer said: "I don't know if it's going to happen.
"If it do, it do - if it don't, it don't.
"They ask me about this fight always, they're always asking me about the fight.
He added: "If Conor McGregor really wants the fight to happen, stop blowing smoke up everybody's ass and sign the paper.
"Sign the paper. You said you were boss - just sign the paper and let's make it happen."
Mayweather, regarded by many as the best pound-for pound boxer of all time, was at the Savoy Hotel in London to promote a match between Gervonta Davis and Britain's Liam Walsh. He has not boxed professionally since in September 2015.
McGregor, 28, was granted a boxing licence in California in December.