Katy Perry admits the beat for 'E.T' was written for a rap group.

The 'Teenage Dream' singer said the idea for the song came from her producers "accidentally" playing her a beat they had designed for southern US hip hop group Three 6 Mafia.

She explained: "I remember writing with Max Martin and Dr. Luke, and they were just showing me different samples of songs or tracks or beats, and they accidentally pulled up this beat, and it was for Three 6 Mafia.

"I heard it and I always knew I wanted to write this futuristic, alienistic song, and I was like, 'Wait, I can wrap my head around this. I know this seems like a long shot, but I think I have the perfect material to put on top of this sound.' And I did, and it really worked out perfectly (sic)."

The single version of 'E.T.' - which stands for Extra Terrestrial - features rapper Kanye West, and Katy admits he helped bring out the track's "urban feel".

She added: "It's kind of a bit harder, it does have that urban feel underneath it. I think that's why Kanye added even another layer on top of it.

"And it has amazing sonics - I mean, there's so much to it, there's a lot in the song if you really put your headphones on and sink into the song."