John Ruiz will defend his WBA heavyweight crown against number one contender Kirk Johnson in Las Vegas on 27 July, promoters announced on Tuesday.

It will be the American's second defence of the title he won by beating Evander Holyfield on points in March 2001.

Canadian Johnson has won 32 of his 33 fights, drawing the other contest against Al Cole in December 1998.

Two other world title fights will take place on the bill at the Mandalay Bay Resort and Casino.

Unbeaten IBF bantamweight champion Tim Austin will make his ninth title defence against Mexican Adan Vargas.

WBA super-middleweight champion Byron Mitchell will also defend his crown for the second time when he takes on Julio Cesar Green of the Dominican Republic.