Howard said he read news reports that money was the issue, saying the contracts he signs apparently "aren't worth the paper that they're printed on sometimes."
Cheadle assumes the role of James Rhodes, a character that becomes Iron Man's sidekick War Machine in the comics, according to The Hollywood Reporter. Robert Downey Jr. will reprise his role as weapons mogul Tony Stark.
Howard, who also starred in "Hustle & Flow," is promoting his new album "Shine Through It."