Katy Perry and Rihanna are in no rush to record a girl power duet - because they want to take their time on the project and release an "iconic" collaboration like Sisters Are Doin' It For Themselves.

The pop star pals have been open about their desire to tackle the charts together, but the I Kissed A Girl hit-maker has high hopes for the track and is eager to emulate the success of the Eurythmics and Aretha Franklin's 1985 hit.

Speaking on Britain's Radio 1, she says, "We've collaborated on a lot of things, but just not songs yet. It's one of those things that's got so much build up that we have to deliver. I want it to be like that Eurythmics and Aretha Franklin song Sisters Are Doin' It for Themselves, not like (Shakira and Beyonce song) Beautiful Liar."

"But I definitely want to do something that is so iconic. (Rihanna's) kind of busy too. 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?

"Sometimes you have to wait for greatness."

Slideshow: Rihanna Lets It All Hang Out