Floyd Mayweather Jr. has agreed to fight Saul "Canelo" Alvarez on Sept. 14 at the MGM Grand in Las Vegas.

"I'm giving the fans what they want," Mayweather said in a message via Twitter.

Mayweather fought May 4 and remained unbeaten with a unanimous decision over Robert Guerrero to retain his WBC welterweight belt. The 36-year-old Mayweather (44-0, 26 KOs) will take on a fighter who is the WBC and WBA light middleweight title holder.

Alvarez (42-0-1, 30 KOs) scored a 12-round unanimous decision over Austin Trout on April 20 to unify the belts.