Christina Aguilera is busy making the promotional rounds for her new gig on NBC's 'The Voice,' but she took some time to talk about her "old friend" Britney Spears, according to OK! Magazine.

Aguilera tweeted a congratulatory message to Spears last week when her album, 'Femme Fatale,' was released but admits she hasn't spent enough time listening to it to comment on it.

"You know what, I haven't heard the whole thing in its entirety," Aguilera said when asked about 'Femme Fatale.' "I've been really hard at work on this show. I haven't had quite the chance to go through the whole thing."

The singer only had nice things to say about her former pop music "rival," however.