James Franco says Selena Gomez was his ''secret weapon'' when filming 'In Dubious Battle'.

The 24-year-old actress and singer stars as Lisa London in the drama movie based on the John Steinbeck novel of the same name, and the feature's director James - who also stars as Mac McLeod - has praised the star as an ''incredibly talented'' actress who ''nailed'' her performance despite being out of her comfort zone.

James said: ''I think Selena is incredibly talented and I don't know what people think, but it seems to me she hasn't done tons of movies like this. She even said that to me when I asked her to do this, she was like, 'Yes, I want to be a part of your world, I want to try it. I'm going to go on this adventure.'

''I felt like I had a secret weapon, that I knew she was a great actress, that people wouldn't be expecting her in this and that I could put her in this and she would nail it. And she did.''

The movie is set during a 1930s labour movement and sees Selena - who was previously known as for her performance in Disney Channel show 'Wizards of Waverley Place' - play a woman who is coached through her brutal birth by Mac and Jim Nolan, played by Nat Wolff.

Speaking about the scene, James told 'Entertainment Tonight': ''She isn't a mother, right, but she did have those instincts. She is like that; she is maternal in a lot of ways.''

''It's a scene from the book and I just thought, if we do this scene, I know Selena is just going to give everything for it. And we did.

''It was almost like a piece of performance art or something like that, we had multiple cameras, we were in there and we just like kept it going. We had a real nurse, we had a real baby, all this stuff and we just kind of did it.''

'In Dubious Battle', which premiered at Venice Film Festival in September, will hit theatres on February 17.