DALLAS: World super featherweight champion Humberto Soto defeated David Diaz by unanimous decision to capture the vacant World Boxing Council lightweight title on Saturday at Cowboys Stadium.

Soto, who already had the WBC super featherweight belt, dropped Diaz once each in the opening and final rounds and raised his record to 51-7-2 to win a 12-round decision by judges' scores of 117-109, 117-109 and 115-111.

Mexico's Soto scored the first knockdown in the first round, flooring Diaz with a hard punch just moments after they clashed heads, opening a cut over Diaz's right eye.

He dropped Diaz again in the 12th with a combination of lefts and rights just before the final bell.

Soto controlled the early rounds but American Diaz, 35-3-1, made him work for the win and seemed to gain strength as the fight progressed.

Sotto and Diaz were fighting on the undercard of the Manny Pacquiao-Joshua Clottey world welterweight championship, the first fight card in the new 1.2 billion dollar Cowboys Stadium.

The crowd of more than 40,000 was one of the largest indoor gatherings in US history for a boxing match.