American Music Awards 2012: Rihanna and Nicki Minaj go head-to-head

There's a showdown brewing between pop singer Rihanna and rapper Nicki Minaj, the top nominees at Sunday's American Music Awards.

But the highlight of the awards show, which begins at 8 p.m. and is being broadcast live on ABC, will be the performances by such stars as Justin Bieber Taylor Swift, Christina Aguilera, Carrie Underwood, Kelly Clarkson, Pink, Pitbull, No Doubt, Usher and Carly Rae Jepsen. All are set to take the stage during the three-hour awards ceremony.

Chris Brown will be performing with Swizz Beatz. And Stevie Wonder, an 11-time AMA winner, is set to provide the soundtrack for a tribute to Dick Clark, who created the American Music Awards in 1973 to pay tribute to modern musicians. Ryan Seacrest will introduce the performers.

Minaj, who tied with Rihanna at four nominations each, will perform her new single "Freedom." The 29-year-old rapper-singer said in an interview that she isn't concerned about the prizes because she doesn't "do music for awards."

This year's 2012 Artist of the Year nominees are Justin Bieber, Drake, Maroon 5, Katy Perry and Rihanna. This year also marks the creation of the new Electronic Dance Music Category. Nominees include David Guetta, Calvin Harris and Skrillex. Winners for all prizes are chosen by online voting by fans.

Sunday's show from the Nokia Theater in Los Angeles will mark the AMA's 40th anniversary.