Just when you thought the lineup for the Billboard Music Awards couldn’t get any bigger, two pop megastars are scheduled to ignite the stage. Beyoncé and Britney Spears will reportedly perform at this weekend’s show.

Sasha Fierce will not only be the recipient of the Millennium Award at Sunday’s ceremony, but viewers will be treated to the first televised performance of her new single “Run the World (Girls).” She performed the song for the first time at Oprah’s farewell show taping earlier in the week. Promos for the awards have been touting her appearance as one that “will leave American talking.”

Her fellow diva Britney Spears will also take the stage, according to Us Weekly. Their sources claim that Brit will join Rihanna for their remix to “S&M,” and appear alongside her “Femme Fatale” tourmate Nicki Minaj for the remix to “Till the World Ends,” also featuring Ke$ha.

While no official announcement has been made, Billboard tweeted, “loving rumors re @britneyspears playing Billboard Music Awds. Better watch Sun 8 PM ABC. Lets say there’ll be surprises.”

Other performers on the bill include Rihanna, Nicki Minaj, Jennifer Lopez, Black Eyed Peas, Cee Lo Green, Pitbull, and Lil Wayne with Mary J. Blige. The 2011 Billboard Music Awards will air live on Sunday at 8 p.m. EST on ABC.