Denzel Washington had to ''lighten up'' for '2 Guns'.

The Oscar-nominated actor is used to playing dramatic roles, so it was quite a challenge for him to embrace the light-hearted nature of his new action-comedy with Mark Wahlberg, according to the film's director Baltasar Kormakur.

He told Empire magazine: ''It was interesting to try to get Denzel to lighten up a little bit, because that hasn't been what he's recognised for. [This movie] doesn't take itself too seriously.''

It appears the veteran actor - who recently earned an Academy Award nomination for 'Flight' - embraced the silliness of his new movie and even suggested scenes in which he and Wahlberg's character fight like little children in the playground.

Wahlberg explained: ''It was Denzel's idea that when kids are fighting, nobody wants to let go or be the first to give up.''

While the action-packed film - which sees the stars play rival government agents forced to work together to solve a major crime - lends itself to a potential sequel, much like action comedies such as 'Bad Boys' and 'Rush Hour', Washington is reluctant about reprising his role.

He said: ''By nature, franchise is a bad word for me. I was asked to do 'Inside Man 2', but it didn't have the magic that the first one had.''

However, Wahlberg - who will star in 'Transformers 4' and a follow-up to hit teddy bear caper, 'Ted' - is more agreeable to a potential sequel.

He added: ''If you can make the second one better or more interesting than the first, great. If not, there's a lot of places you can go to get a pay cheque.''