Unbeaten US boxing star Floyd Mayweather announced Wednesday he will fight Puerto Rico's Miguel Cotto on May 5, ending hopes for a showdown with Manny Pacquiao before November.
Mayweather will step up from the welterweight ranks and fight for Cotto's World Boxing Association super welterweight crown in Las Vegas before he begins a 90-day jail sentence on June 1 after a domestic violence conviction.
Boxing fans have long sought a matchup between Mayweather and Filipino icon Pacquiao. Mayweather even made a Twitter challenge for the Asian star to "Step Up, Punk", but they could not work out a deal so Mayweather went to Cotto.
"Miguel Cotto is a world class fighter who can never be taken for granted and continues to prove he is one of the best in boxing," Mayweather said.
"It will be a challenge for me to compete with him at this weight, but this is the type of test I thrive on and gives me the motivation to train even harder. I have no doubt in my mind that my title belt collection will increase once again and Cotto's reign as champion will come to an end on May 5."
Mayweather, who has won titles in seven weight classes, won his only other fight at super welterweight in 2007 with a split decision over Oscar de la Hoya for the World Boxing Council title.
Cotto defended his crown last December by stopping Antonio Margarito in the 10th round.
"I am here to fight the biggest names in boxing," Cotto said. "I've never ducked anyone or any challenge in front of me. I have accepted everything to give the fans what they like - great and exciting fights.
"Stay tuned because I will convincingly beat Floyd Mayweather."
Mayweather had made a deal for a May 5 fight but Pacquiao had wanted a June date to maximize revenue for what figures to be the biggest-paying blockbuster in boxing history, if it happens, which now cannot happen until late this year.
Pacquiao is still deciding who he will face in a fight to be staged in May or June.
Cotto and Mayweather have agreed to Olympic-style drug testing for the fight. Mayweather's insistence on such methods helped scuttle prior talks for a Pacquiao fight.
Mayweather, 41-0 with 25 knockouts, won his last fight in controversial fashion, knocking out Victor Ortiz last September when his rival was distracted by the referee having just restarted the action after a break.
Cotto, 36-2 with 29 knockouts, is 16-2 in world title fights and avenged a 2008 title loss to Margarito two months ago.