Bradley Cooper and Lady Gaga. Picture: Warner Bros.

Lady Gaga and Bradley Cooper have unveiled their 'A Star Is Born' duet, titled 'Shallow'.

The duo - who star as struggling singer Ally and seasoned musician Jackson in the hotly-anticipated movie - have showed off their brand new power ballad, which Gaga penned with Mark Ronson, Andrew Wyatt and Anthony Rossomando. The song was co-produced by Benjamin Rice.

Speaking about how the track came about, she said: "I think things come in sequence and artists, you know, I think that we move to a certain cadence in a sequence in the way that we want to put things into the world that we believe in. 

But especially with the song 'Shallow' being such a crucial moment in the film you know. I did work on 'Joanne' with Mark Ronson and I worked on 'Shallow' with Mark Ronson and Andrew Wyatt and Anthony Rossomando. And we made this song for Ally and Jack and it's such a special song you know. It's two people talking to each other and talking about the need and the drive to dive in to the deep end and stay away from the shallow area."

And Lady Gaga confessed she was "blown away" by Bradley's voice when she first heard it.

She told Zane Lowe on Beats 1: "I was blown away by it, you know, because the truth is that there's people that can technically sing perfectly and have no soul. And with Bradley, he just sings from his soul and he knows how to tell a story when he's singing and I heard it right away. And I knew in that moment - you know, I'm kind of a bit of a snob when it comes to watching actors play rock star, but I'm telling you, I was like, this man knows how to be a rock star.