Sugar Shane Mosley has vowed to send Floyd Mayweather Jr back into retirement when the two clash in Las Vegas on May 1.

The 38-year-old (46-5) is training in the mountains of California and is looking to recapture the form that brought him world titles at three different weights.

Mayweather, unbeaten in all 40 of his professional contests, is widely regarded as the best pound-for-pound fighter in the world, but Mosley is confident of victory next month.

"I was 38-0 with 35 knockouts when I stepped into the ring and lost for the very first time," said Mosley, the current WBA welterweight champion .

"So when you say 40-0, that doesn't mean a thing to me. All it means is that I'll be the one giving him his first loss.

"No disrespect, but I really don't think he's been in there with a fighter like me, and I believe that when I beat Floyd, I will send him into retirement. May first will be May's first loss."

Mosley, who defeated Antonio Margarito in his last fight back in January 2009, claims his training and sparring could not have gone better.

"Right now, my weight is great. I'm probably weighing around 152-ish when I leave the gym," added the five-time world champion.

"I look at Floyd as a natural welterweight - a real 147-pounder. In fact, Oscar de la Hoya is the biggest guy that he's fought that was a big welterweight, and Oscar did well against him.

"I'm pretty sure that Floyd will feel more power in this fight that he will have ever had to feel. And if I can get that knockout, if I get that one shot, and if I can get him hurt, then I'm going to be all over him."