The 'Firework' singer - who split from husband Russell Brand in November - was asked if she would ever collaborate with her close friend and though she ruled out working on a record with the star, she joked that they would do something more intimate instead.
She joked to US radio station Wild 94.9: "No, but we're going to have s*x."
Katy was also asked if she listens to her own music when she is having s*x and said it would be "over the line".
She said: "I'm not a narcissist! OK, I'm a narcissist, but that would be over the line.
"Having s*x to your own song, that's horrible. I'm a good Christian girl."
The raunchy conversation continued with Katy questioned on whether she has ever had a threesome but the star would only say "no comment".
Despite her jokes, Katy has previously confirmed she will collaborate on a song with Rihanna but wants to make sure it is "iconic".
She said: "It's one of those things that's got so much build up that we have to deliver...I definitely want to do something that is so iconic.
"We're both busy but we planted the seed two years ago. How disappointed would you be if that song came out and it's no good?"
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