Manny Pacquiao has warned Floyd Mayweather not to underestimate Miguel Cotto when the two meet for their scheduled fight in Las Vegas in May.

Cotto faced Pacquiao in 2009 and lasted nearly the whole bout before being stopped in the 12th round.

"He thinks that Cotto is an easy opponent, but he's not. Cotto is a good boxer, he's strong. He needs to train hard, because Cotto is strong, very strong," Pacquiao told boxingscene.com.

Despite the warning, Pacquiao's coach Freddie Roach has revealed that he hopes Cotto can beat Mayweather in May.

Roach said: "I don't think Mayweather can knock him out. I hope Cotto does well. I hope he gets one in and knocks him out and just shuts this guy up. Somebody's got to shut this guy up."

Pacquiao faces Timothy Bradley in June.