For unknown reasons, Canadian singer Justin Bieber suddenly issued a challenge to Tom Cruise to face him in an MMA fight.

The 25-year-old pop star also tagged UFC president Dana White to host the fight inside the Octagon.

"I wanna challenge Tom Cruise to fight in the octagon. Tom, if you don't take this fight, you're scared and you will never live it down," he tweeted on Monday.

Following the tweet, former UFC two-division champion Conor McGregor, true to his 'Notorious' nickname, chipped in and offered to be the middle man for the fight if the 56-year-old actor, known for his roles in various films such as Mission: Impossible, Jack Reacher and Top Gun, accepted Bieber's challenge.

McGregor then doubled down by challenging another actor, Mark Wahlberg, to fight him on the same card.

Wahlberg previously said he would give a piece of his stake in the UFC to the Irishman after the latter beat Eddie Alvarez in 2016, but he later retracted the offer.

Neither Cruise nor Wahlberg had responded to the challenges at the time of writing.