Pound-for-pound king Floyd Mayweather will face THE RING junior middleweight champ Saul Alvarez on Sept. 14 at MGM Grand in Las Vegas on Showtime Pay Per View, Golden Boy CEO Richard Schaefer confirmed to RingTV.com on Wednesday evening.

The bout will take place at a 152-pound catchweight, which means Alvarez will have to weigh-in two pounds under the junior middleweight limit of 154 pounds the day before the fight, which is easily the biggest boxing event scheduled for 2013.

“It’s accurate. The fight is done. It’s going to be the biggest one that we’ve promoted so far. It’s the one fight that everybody wants to see, and it’s the one that we’ve been working on very, very hard, so it’s done. The fight is on,” Schaefer told RingTV.com.

“It’s going to be at 152. It’s going to be for all of the belts,” comprised the WBA and WBC 154-pound titles, as well as Alvarez’s RING championship.

Mayweather (44-0, 26 knockouts), THE RING’s welterweight champ, announced his decision on his Twitter account on Wednesday night.

“I chose my opponent for September 14th and it’s Canelo Alvarez,” wrote Mayweather. “I’m giving the fans what they want. It will be at the MGM Grand.”

Mayweather is coming off a one-sided unanimous decision over Robert Guerrero on May 4. The undefeated future hall of famer had targeted to fight twice in 2013, both times on the weekends of Mexican holidays — Cinco De Mayo and Mexico’s Independence Day — in order to maximize public interest and pay-per-view buys.

Thus, the choice of Alvarez (42-0-1, 30 KOs) comes as no surprise. The unbeaten 23 year old, known as “Canelo” to his fans, is the biggest boxing star in Mexico and one of the best ticket sellers among prize fighters in the U.S.

With very little time to promote the event, Alvarez drew close to 40,000 fans to the Alamodome in San Antonio on April 20 when he defeated previously unbeaten contender Austin Trout via unanimous decision.

The Tim Bradley-Juan Manuel Marquez fight, which was scheduled for Sept. 14 in Las Vegas, has been moved to Oct. 12 at the Thomas & Mack Center, Top Rank CEO Bob Arum has informed RingTV.com. Presumably, the move was so the two pay-per-view events (Mayweather-Alvarez on Showtime PPV; Bradley-Marquez on HBO PPV) would not conflict.

More on this story as it develops.

Photos by Naoki Fukuda

Lem Satterfield can be reached at [email protected]