Rihanna is planning a big "surprise" for Chris Brown's birthday.

The 'Diamonds' singer wants to prove her love for the 'Yeah 3x' hitmaker and plans to go all out to help him celebrate turning 24 on May 5.

Speaking about her plans, a source said: "It's a surprise. All I can say is she's got a few things up her sleeve. She wants Chris to know how much she loves him and wants him and honestly, she just wants to be with him and let him know she's got his back."

However, Rihanna's plans may not come to fruition as she has a gig scheduled in Brooklyn on Chris' birthday and doesn't want to force him to fly into New York to be with her.

The source added to HollywoodLife.com: "Chris treated her so bomb and surprised her with his presence when she turned 25, she wants to be with him badly when he turns 24.

"She's not going to flat out ask him to be with her - not on his birthday because she feels that's his day - but in her heart she wants him with her."