LAS VEGAS - Unbeaten US fighter Tim Bradley, unable to reach terms for a unification showdown with England's Amir Khan, will defend a world junior welterweight crown on next month's Manny Pacquiao card.

Pacquiao's promoters, Top Rank, announced the signing of Bradley on Wednesday and his November 12 defence of the World Boxing Organisation title against Cuban southpaw Joel Casamayor, a former Olympic and world champion.

Pacquiao's world welterweight title defence against Mexico's Juan Manuel Marquez will headline the fight card in Las Vegas.

Bradley, 27-0 with 11 knockouts, stopped Devon Alexander in the 10th round in January in a showdown of unbeaten US fighters to unite the WBO and World Boxing Council crowns.

But Bradley was unable to agree terms for a fight with Khan, who owns the division's World Boxing Association and International Boxing Federation titles, to determine an undisputed junior welterweight world champion. Instead, Bradley kept the WBO title, Khan will defend his crowns against American Lamont Peterson in Washington in December and Mexico's Erik Morales won the vacated WBC belt last month.

Bradley, 28, won his first world title by winning a split decision over Britain's Junior Witter in 2008. Casamayor, 40, has a record of 38-5 with one draw and 22 knockouts. He was a super featherweight world champion in 2000 and 2001 and won the WBC lightweight title in 2006. He won the 1992 Barcelona Olympic bantamweight title.