Los Angeles, Feb 7 : Singer Mariah Carey has warned pregnant singer Beyonce Knowles that carrying twins is "hard".

Carey is thrilled that her friend is expecting two babies with husband Jay Z, but found during her own experiences carrying her and former spouse Nick Cannon's children Moroccan and Monroe, 5, that a multiple pregnancy takes its toll.

"The last time I saw her, I was doing my Christmas (show in New York), and she came to my show and brought her daughter. It was really, really sweet," Carey told etonline.com.

"I just wish her and Jay all the best. It's really hard having twins. I just mean in general, going through the physicality of having twins was really, really difficult for me. I had a tough time," she added.