Justin Bieber wasn't serious about taking on Tom Cruise in a fight, or maybe he's simply changed his mind ... because he says Tom would kick his ass!
JB played it cool for the paps in L.A. Wednesday as he was leaving Hailey's fashion line office, telling them he was just goofing around when he randomly challenged the 56-year-old actor to an MMA fight and asked Dana White to make it happen.
He says he had just seen an interview with Cruise so he was on his mind, and decided to tweet out the bizarre challenge .