LAS VEGAS — Floyd Mayweather Jr. finalized a deal to fight Sugar Shane Mosley on May 1 in a welterweight bout at the MGM Grand Garden in Las Vegas.

Mayweather (40-0, 25 KOs) agreed to the bout last week, but formally signed the contract on Wednesday for the former pound-for-pound champion's second fight back from a brief retirement.

"This one is definitely for the fans, as I wasn't going to waste anyone's time with a meaningless tuneup bout and asked to fight Shane immediately," Mayweather said. "I have said ever since I came back to the sport that I only wanted to fight the best. I think Shane is one of the best, but come May 1, he still won't be great enough to beat me."

Although the fight is an intriguing matchup between two veteran welterweights who have been circling each other for a decade, the dangerous Mosley (46-5, 39 KOs) still wasn't Mayweather's first choice.

Mayweather agreed to the bout only after several weeks of negotiations with Manny Pacquiao failed to produce an agreement on what's likely to be the richest fight in boxing history, if it ever occurs. Pacquiao balked at Mayweather's stringent drug-testing demands, and instead will fight welterweight Joshua Clottey on March 13 at Cowboys Stadium.

Mayweather and Mosley agreed to participate in Olympic-style drug testing for their fight, saying they hope to set a new standard for safety in boxing. Mosley has acknowledged using steroids before a victory over Oscar De La Hoya in 2003, but claims he did so inadvertently through a coach who had connections with the BALCO lab.

"I'm real disappointed and real angry to be linked to juicing and steroids, because that's just not me," Mosley told The Associated Press in a phone interview. "I don't need to do that stuff. I like the testing for this fight. I want it, because I want to prove that everything I've done is all me, and not about steroids. I've never tested positive for anything, but I want everybody to know who I really am."

Mosley was scheduled to fight Andre Berto on Jan. 30 at Mandalay Bay Casino before Berto dropped out while dealing with the earthquake in Haiti, his family's home. Mosley expressed only sympathy for Berto's family, but the setback quickly evolved into a chance for a major bout.

"I knew that there was a fight around the corner," Mosley said. "I knew that Mayweather needed a dancing partner, and who else was he going to dance with? I'm a little stronger and wiser now. I'm very smart. Nothing he can do is going to rattle me and make me feel any different. I'm already in good shape, and I'm going into it feeling good."

Mosley, the 38-year-old WBA welterweight super champion, has been vocal about his desire to meet Mayweather ever since Mayweather celebrated his ring return last September with a one-sided victory over Juan Manuel Marquez. Mosley, a partner in Golden Boy Promotions, jumped into the ring after Mayweather's win and taunted the unbeaten fighter.

But Mayweather appeared to be focused on the biggest payday of all against Pacquiao until his hard line on drug testing scuttled the fight.

Mosley formalized his commitment last Friday but Mayweather didn't sign the deal for five days, prompting worries for Mosley's management and Golden Boy CEO Richard Schaefer, who represented Mayweather throughout the torturous negotiations with Pacquiao's promoters at Top Rank.

Just a few days ago, Schaefer publicly acknowledged he was worried Mayweather might be having second thoughts about a tough fight against Mosley, who has only improved with age.

Mosley's only loss since late 2004 was a narrow decision to Miguel Cotto in November 2007. He has fought just twice since then, stopping Ricardo Mayorga and former champion Antonio Margarito, although Mosley was scheduled for fights against Zab Judah and Berto that were canceled by his opponents.

Mayweather should have the services of Roger Mayweather, his uncle and longtime trainer. Roger Mayweather has a June 1 trial date in Las Vegas on several serious charges related to accusations of beating and choking a female boxer last summer at an apartment he owned. (AP)