Rihanna wanted to duet with Chris Brown because he is ''dirty'' and shocking.

The 24-year-old singer chose her ex-boyfriend and rapper - who was convicted of assaulting her three years ago - to collaborate with on her hit single 'Birthday Cake' because she thought it would be ''cute'' to team up with a man.

She said: ''I thought it would be cute to do it with a guy. I wondered, who can be dirty, someone who people will really believe?''

Rihanna and Chris have made peace since 2009's altercation, and while she understands people have ''every right to be concerned'' about the pair working together, the brunette beauty insists her fans are keen for them to collaborate again.

Speaking in an interview with Harper's Bazaar, she added: ''Look, I understand that people had every right to be concerned about it. But I didn't see it that way because I'm in a different place.

''Music is music and my fans have been asking me to record with him. I just felt like it was time. It was time.''

As well as her fans, Rihanna's father Ronald Fenty is also keen for the former couple to hook up again.

He recently said: ''Chris has matured a lot. I think everybody has to put the past behind them. And they seem to have done that. Being a couple is all up to her.

''Every decision is her decision. I just wish her the best. I hope things will work out.''