Pop singer Christina Aguilera declared she was overjoyed when she heard that her rival, pop princess Britney Spears gave birth to a baby boy.

Aguilera, 25, who used to sing with Britney at The Mickey Mouse Club and portrayed as pop rivals, confessed she didn't pay too much attention to Britney's pregnancy, but now she is "overjoyed and thrilled" for her.

She said: "My assistant came in the room when it happened and she's like, 'Britney had a boy!' and I was like, 'Oh my gosh!'

"I don't know where I was for a while when she was pregnant but it really kicked in at that point," she declared for the Us Weekly US Weekly "Young Hollywood Hot 20" event on Friday.

"It's like, wow, she had a baby! That's crazy! I'm overjoyed and thrilled for her," said Aguilera.

She added: "It's such an exciting time in her life and I just wish her the best."

Christina Aguilera, born December 18, 1980, in New York, is most often recognized by her notable vocal abilities and unorthodox fashion sense.

Her vocal skills have been compared to those of singers such as Mariah Carey and Whitney Houston, and she is one of the most prominent recording artists of her generation.

Christina has achieved four number-one singles on the Billboard Hot 100 chart, as well as two top five albums and four Grammy Awards in the United States.