Hamed's third fight in America would thus be held a week before the heavyweight unification re-match between Lennox Lewis and Evander Holyfield, scheduled for 13 November, at the Thomas & Mack Centre in Las Vegas.
Soto's promoter, Bob Arum, said that a hitch had arisen over a return clause. The Mexican's financial details have been settled, but Arum said that there was a problem over the Hamed camp's desire for a re-match. "I think they want an immediate re-match, but that's contrary to the rules of the organisations. That is something that has got to be sorted out," Arum said.
Joe Calzaghe, meanwhile, will make his American debut on the same promotion as boxing's richest non-heavyweight fight. The WBO super-middleweight champion has been lined up to defend his title on the Oscar De La Hoya- Felix Trinidad undercard at the Mandalay Bay resort in Las Vegas on 18 September.
Calzaghe's promoter, Frank Warren, and De La Hoya's handler, Arum, have still to sell the show to Sky but are confident it will be shown in Britain by the satellite network. Calzaghe was disappointing in his last defence against Australia's Rick Thornberry, which went the distance, but the Welshman was troubled by an injured hand and needed a painkilling injection in an elbow before the bout.