Rihanna thinks that Katy Perry and Russell Brand are perfect because they're both "hilarious, rude and disrespectful."

The 'Rude Boy' singer - who is expected to be bridesmaid when the couple marry later this year - became friends with the singer and the comic separately, but admits she would never have predicted they would embark on a relationship 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.' "

Though Rihanna is outspoken about Katy and Russell's relationship, she is more tight-lipped about her own romance with American baseball player Matt Kemp, who she has been dating since the beginning of this year.

The 22-year-old pop star said: "We are not in an official couple or anything. He is nice."