The `California Gurls` hitmaker - who is engaged to British funnyman Russell Brand - envies her pal?s curvy figure so much, she wants her to show it all off in a raunchy dance at her all-female pre-wedding party.

When asked how much she wants Rihanna to show, the singer replied: "The whole bit, the whole bit.

"She`s gonna get the message - she`s hot I love her and she`s the coolest chick and I want all of her curves and we have a lot in common."

The singer also admitted Rihanna put herself in charge of organising the evening without even having to be asked.

She told Chicago?s Kiss FM radio station: "That`s the one thing I don`t have to plan and I`m really excited about it."

Rihanna has given the couple her blessing in the past - but also admitted she never thought the pair would end up together.

She said: "I met him a few years ago when he interviewed me, and became friends with Katy later, and it`s so funny because I would never have put the two of them together.

`But when she told me it made so much sense. I was like, `Of course you guys would be together, you are both just hilarious and rude and disrespectful, it`s perfect.` "
sections: Celebrities