Russell Crowe says the hardest part about being an actor is not being around his sons.

The 'Noah' star finds himself away from home for much of the year due to his busy acting schedule, and admitted he is finding it ''harder and harder'' to take new roles because he hates leaving his children, Charles Spencer Crowe, 10, and Tennyson Spencer Crowe, eight.

In a conversation on upcoming Foxtel Bio show 'The Truth About Us', he confessed: ''It absolutely drives me crazy, the tension that I live with... when I get on that plane, because I'm not able to get to them in five minutes if they need me.

''It gets harder and harder.''

The actor - who turned 50 earlier this year - separated from the children's mother, singer-songwriter Danielle Spencer in 2012, and explained family life has been more difficult than he expected.

He continued: ''For me, the choice of having children was not about the fact that I would be leaving them to go off overseas,

''I always just somehow ­assumed we'd be like other showbiz families and we'd always work out a way of being together.''

The 'Man of Steel' star added that his wish to be nearer his sons - who now live with their mother in Sydney - has even meant he is becoming more apprehensive about taking overseas movie roles.

He said: ''Since the boys stopped travelling, it's had a wonderful effect on them -- the fact that they have a constant life,

''But it's really difficult, I've got to find more things to do at home because it's where I should be now -- I need to be where they are.''