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The lineup just keeps getting better for this year's American Music Awards ... with Justin Bieber and Christina Aguilera added to the show. Gonna get dirrrrrrty!

Biebs and Xtina join fellow entertainers Maroon 5, Kelly Clarkson, Mary J. Blige, Pitbull and Katy Perry.

Larry Klein, the show's producer, revealed that Aguilera will be hitting the stage with Adam Levine to sing "Moves Like Jagger."

The AMAs will air November 20 on ABC.