Bradley Cooper and Lady Gaga in 'A Star is Born'.

Lady Gaga and Bradley Cooper have struck up "a lifetime friendship".

The two stars made waves on the big screen in 'A Star Is Born', and now the 32-year-old singer and actress has revealed the most rewarding part of the whole experience is the way their relationship has continued after the movie.

She told 'Entertainment Tonight': "We talk all the time, yeah. And it's exciting and wonderful and we are both so grateful for how the film is being received...

"You know, that's what's really come out of all of this for me: the reward of a lifetime friendship with someone I deeply respect."

The 'Bad Romance' hitmaker recently admitted the role of hopeful singer-songwriter Ally in the blockbuster was a "big dream" come true, as she wanted to be an actress long before she was a singer, and even creates characters for herself when she's on stage.

She said: "I wanted to be an actress before I wanted to be a musician, so this was a big dream of mine. I felt really excited and really ready for this part.

"[I have] created characters [onstage] because I did not make it as an actress, so I made characters that I could be - so I could be one. They were always some way related to the woman that I wanted to sing to, and a part of me."

Gaga previously revealed she even sneaked into a local cinema to watch the movie - which sees her star as Ally opposite Bradley Cooper's rock star Jackson Maine in the modern remake of the 1936 classic - but she was so "emotional" she had to leave.

She admitted: "Yeah, I snuck in. I sat through most of it. I had to remove myself before the end. The film moves me so deeply.

"I feel so entrenched in the character that the second half of the film - without revealing what happens - is so emotional and tragic. I have to take myself out of it."