It's ON in the Octagon!

Looks like Justin Bieber and Tom Cruise are one step closer to meeting in the ring after the pop star challenged the 56-year-old Mission Impossible star to a boxing match earlier this month on Twitter.

Last week, UFC reps and CEO Dana White were apparently on a phone call with Scooter Braun, Justin's manager, discussing the possibility of this epic fight, according to TMZ and everyone was down with the idea ... now they just have to get Cruise on board!

According to the report, William Morris Endeavor honcho Ari Emmanuel said he thinks Tom will agree to take on Justin. So SOMEBODY better pick up the phone and make this happen!

Watch our video, below, of Justin explaining his challenge to Tom Cruise ...