Undefeated world welterweight champion Floyd Mayweather will fight Andre Berto next month as he seeks to equal Rocky Marciano's 49-bout undefeated record, he announced. Mayweather, 38, who holds the WBA and WBC titles but had to give up his WBO belt last month, will face fellow American Berto on Sept. 12 in Las Vegas. He is expected to retire if he wins the match.