Justin Bieber is convinced One Direction decided to release their album on the same day as his as a publicity stunt.

The two acts will go head-to-head in the charts when Justin's follow-up to 2012's Believe is released on the same day as the group's fifth album.

Justin is certain One Direction decided to drop Made in the A.M. on 13 November (15) so they could drum up publicity for themselves.

"I don't know if they're really going on the road (to promote) much but we're talking about them right now so it gives them some promo right? So, that's probably why they did it," he says during an interview on New Zealand radio station The Edge.

"I think it was strategy on their part because my release date was first."

He insists he is not worried about their "friendly competition", adding, "But whatever... It's going to be fun. I'm excited to see what happens."

Justin first joked about their chart battle in a Snapchat video last week (ends04Oct15) in which he said, "The face you make when you come out with an album the same day as Justin Bieber" before pulling a horrified expression.

His album is believed to be called Purpose.