Bradley Cooper admits his directorial debut was a huge risk.

Bradley Cooper

Bradley Cooper

The 43-year-old star moved behind the camera for the first time to helm the musical romantic drama 'A Star Is Born', and Bradley - who also appears in the movie - has admitted he placed a massive amount of trust in his co-star Lady Gaga.

Bradley confessed: "The thing that I was very aware of from the beginning and I cherish even to this day is how much we both had at stake, because it was a first for both of us.

"We knew that going into it, we were really going to have to rely on each other, because it's scary putting yourself out there to this degree."

Gaga - who previously starred as the Countess on 'American Horror Story: Hotel' - admitted it was "incredible" to watch Bradley on the set of the film.

She told E! News: "Just watching him direct, watching him write, watching him write, not just the screenplay, but watching him write music for himself, becoming a musician, seeing him create his character and him guiding me through the process. It was just incredible."

Bradley recently admitted that directing 'A Star is Born' was a "very cathartic" experience.

The drama movie tells the story of a hard-drinking country musician, and Bradley confessed that making the film was a freeing experience for himself.

The Hollywood star - who has previously admitted to struggling with drugs and alcohol - said: "Anytime you're trying to tell the truth you need to go to places and use things that have happened to you, or you've read about or experienced.

"And that's all part of the beauty of turning whatever things you've gone through into a story. I find that to be very cathartic. I remember learning that in grad school, our teacher said all the insecurities, all the dark stuff you get to use that and that's really the truth."