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.

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

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. "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."