Mayweather Jr and Marquez visited London in May to promote their fight
Floyd Mayweather Jr's comeback bout against Juan Manuel Marquez has been rescheduled for 19 September.
The undefeated five-weight champion was due to fight Mexico's Marquez on 18 July but pulled out with a rib injury.
Mayweather has not fought since beating Britain's Ricky Hatton in a December 2007 welterweight bout.
"I will destroy Marquez and reclaim my rightful place as boxing's pound-for-pound king all in one night," said the 32-year-old.
"I am relieved to be cleared to fight as I was already looking forward to getting back in the ring."
The 12-round bout will be staged at the MGM Grand in Las Vegas as originally planned.
It is seen as a stepping stone for Mayweather to an eventual showdown with Filipino star Manny Pacquiao, his successor in the pound-for-pound rankings.
He will fight Marquez - the WBO and WBA lightweight champion - on the weekend after Mexican Independence Day.
"I am happy that Mayweather has been cleared to fight and we can get down to business," said Marquez, nicknamed 'Dinamita'.
"I will be fighting for (people) who will have a great reason to celebrate my win over Mayweather, which will be for the entire country of Mexico. I am sure of victory."
Mayweather has won all 39 of his professional contests, with 25 victories coming via knockouts.
Marquez, 35, has won 50 of his 55 fights (37 by KO), with four defeats and one draw.