Bradley Cooper will be singing as himself at the Oscars - not his 'A Star Is Born' alter-ego Jackson Maine.

The 44-year-old actor and Lady GaGa - who played lovers Ally and Jackson in the musical blockbuster - will perform the Oscar-nominated song 'Shallow' at the ceremony at The Dolby Theatre in Los Angeles on February 24, but Cooper has admitted he won't be able to use his gravely southern drool as it's ''gone''.

Appearing on 'The Late Show with Stephen Colbert' on Thursday (14.02.19), he said: ''He's (Jackson) gone. I am not going to try and get him back.

''But I will be me singing.''

However, he is making sure he hits the notes by rehearsing with his vocal coach from the movie.

He said: ''I'm going to start rehearsing with this great vocal coach who I love, Roger Love, who I worked with all the time on the movie.

''I hope to be in present and enjoy it and hopefully people love the song sung that night.''

The 'Burn' actor recently performed the song with the 'Born This Way' star at her Las Vegas residency show, but he pretended to act like a rock star because he ''certainly isn't'' one.

He said: ''The truth is as was revealed when I went on stage at Vegas, I had to create a character because that guy certainly isn't a rock star.

''She asked me to come up on stage at her incredible residency that she is doing for two years that you should all go and see and the jazz show, which you've got to go see, one night she does which is amazing.

''So I went up there and watch the video back and we went up there and sang it and I just sort of look like this idiot from Philadelphia singing with Lady Gaga...

''Luckily I was on pitch and thank God, but I was like, 'Oh, Jackson's gone.'''

Cooper - who also directed the movie - admitted that the thing he was ''most terrified'' about was getting the accent right, and he stole aspects of his co-star Sam Elliott's (Bobby) voice.

He said: ''Part of when I was knowing I wanted to do this morning and wanting to sing everything live, I had to create these guys, and I am sure you've had them, but they are so idiosyncratic and iconic, they are like the rock stars.

''So one of the things I knew I wanted to do, was to lower my voice.

''But I didn't want to make it too country and Sam Elliott is from Sacramento, but his mother was from Texas, so he has this accent that you can't quite place, but it's so wonderfully iconic.''

The 'Limitless' star said that he would go to sleep with a sore throat after practicing.

He said: ''First of all I would do this warm up all the time ... I don't think I could. The first six months I could only do it like this (with his head down).

''I would go to sleep and my throat would hurt and I thought, well this is never going to happen.

''That is what I was most terrified of, this voice.''