Jack Black has compared President Donald Trump to ''Charlie Sheen on crack''.

The 'Polka King' actor mocked the US leader for his ''obsession with winning'' and compared him to the troubled 'Anger Management' actor, who suffered a highly-publicised meltdown in 2011 which saw him fired from 'Two and a Half Men' amid bizarre public behaviour, wild partying and proclamations such as being a ''warlock'' with ''tiger blood'' who was ''winning''.

Speaking during an interview at the Variety Studio presented by Orville Redenbacher at the Sundance Film Festival, he said: ''We've got to start thinking globally. We're going to be working together, if we're going to survive, if the human race, if this species is going to survive.

''Yeah, America first is fine, in terms of finances, but we've got to stop thinking that way. It's not a Monopoly game where the rich billionaire wins the game. It's about the world working together, and it's got to happen soon.''

His co-star Willie Garson then commented: ''This whole concept of winning, what do you mean winning? At the expense of what? Winning, implied, is someone losing ... this is insanity.''

Jack quipped in response: ''Who else has been talking about winning obsessively lately? Oh yeah. Charlie Sheen. When he was on crack.''

And as his castmates and directors laughed, the 47-year-old star admitted it was a scary suggestion to think the former 'Apprentice' star and the 'Young Guns' actor were ''on the same exact page''.

He joked: ''Where are we where the president and Charlie Sheen are on the same exact page?''

Charlie previously blamed testosterone cream for his public outburst.

He said: ''That was a very specific period of time that did feel very out-of-body and very just detached from all things real.

''I felt superhuman during some of that.

''It was a lot of highs and lows. I was taking a lot of testosterone cream, and I think I went too far with it. It was kind of like a borderline . . . not a 'roid rage, but a 'roid disengage.''