Vitali Klitschko was thought to be keen to fight Briton David Haye
WBC heavyweight champion Vitali Klitschko will defend his title against American Chris Arreola on 26 September.
Klitschko, 38, has set up the bout after a prospective fight with Briton David Haye failed to materialise.
"Arreola is one of the toughest opponents," said Klitschko. "He's young, undefeated, has a powerful punch and is confident.
"I won't underestimate him but I have no doubt that I will leave California as world champion."
With Arreola hoping to become the first Mexican-American to win a major heavyweight title, a large crowd is expected at Los Angeles' Staples Centre, especially as Klitschko has spent spells living in the city.
Klitschko has 37 wins and two defeats in his career, while 28-year-old Arreola is undefeated, with 24 of his 27 wins via knockout.
"To fight the world champion in my hometown, this is a dream come true. The chance of a lifetime," added Arreola.