Paul Walter Hauser has apologised for his "needlessly mean-spirited" comments about Vin Diesel.

The 37-year-old actor took a swipe at the 'Fast and the Furious' actor - who he has never met - a few weeks ago for allegedly behaving unprofessionally on set, but he's now admitted he should never have "shot [his] mouth off" and behaved unfairly towards a fellow professional.

However, the 'Black Bird' star seemingly stood by the content of his remarks as he didn't backtrack on what he had said.

He wrote in a lengthy post on Instagram: "A few weeks back, I made a random comment about Vin Diesel. It started somewhat humorous, but unraveled into me dogging him out over behavior I had heard about on multiple occasions from multiple sources.

"I had done a night shoot on a Friday, gotten 1 hour of sleep, and then flew to LA from ATL at 6am to do a full day of press for Inside Out 2. I was exhausted and, in my fatigued state, I shot my mouth off and made a careless, needlessly mean-spirited, comment. That comment was recorded and then went viral.

"Just here to say that I am sorry for having made that comment. I do indeed get riled up by some of the behavior I’ve witnessed, or heard about, and “outing” people to any extent can feel momentarily satiating.

"I no longer feel that way and am genuinely sorry for shooting my mouth off and not showing love to Vin, who I do not know and have never met. It isn’t fair of me to make judgments of that kind, and even if some of those things turned out to be true, it is mean to shout them out and playfully attack someone.(sic)"

Paul further reflected on his own behaviour and offered a direct apology to Vin.

He wrote: "As a self-professed Christian, I need to do a better job of loving people and not trying to “right a wrong”, or allow my ego to posture itself with some sort of verbal flex. It just isn’t additive to our culture, and it can hurt other people.

"@vindiesel - I apologize. Thank you for entertaining so many people and making them happy. I’m trying to do the same.

"Time for me to be quiet. I sometimes talk myself into idiocy.(sic)"

Paul's original comments came when he was left unimpressed when an interviewer compared his 'Inside Out 2' character Embarrassment to Groot, who is voiced by Vin in the 'Guardians of the Galaxy' films.

The CinemaBlend reporter said: “You’re like Vin Diesel now."

The 'Cruella' actor replied: “Please don’t say that. I like to think I’m on time. And approachable.

"I love people but when I hear stories about Hollywood actors who get paid really well and mistreat people, I out them constantly. And it’s a blast.”