By Dean Goodman

LOS ANGELES - Country star Taylor Swift and Michael Jackson each won four prizes at the midway point of the American Music Awards on Sunday, while Jennifer Lopez fell on her rear end during her performance.

Swift and Jackson lead the contenders at the 37th annual ceremony, with six and five nominations, respectively, and will vie for the event's final honor, artist of the year.

Swift, 19, accepted her awards live via satellite from backstage at London's Wembley Arena, where she will perform a concert on Monday.

She was named favorite female artist in the pop/rock and country categories, and favorite adult-contemporary artist - tributes to her wide crossover appeal.

Her 2008 album "Fearless", the best-selling release in the United States this year, was named favorite country album.

Jackson was named favorite male artist in the pop/rock and soul/R&B categories. His brother Jermaine accepted on his behalf, thanking Allah "for blessing my entire family."

The singer, who died of an overdose in June, also won two awards that were announced off the air. His hits collection "Number Ones" was named favorite album in the soul/R&B and pop/rock categories, beating out Swift in the latter.

The other contenders for artist of the year are glam pop star Lady Gaga, rapper Eminem and rock band Kings of Leon. Hip-hop act the Black Eyed Peas won two awards, as favorite group in both the pop/rock and soul/R&B categories.

Punk rock trio Green Day was named favorite alternative artist. Rascal Flatts won favorite country group for the fourth year in a row.

Keith Urban won the first American Music Award of his career, for favorite male artist in the country category. He dedicated his award to his wife, actress Nicole Kidman, and their daughter Sunday.

Hip-hop couple Jay-Z and Beyonce each won an award; he for favorite rap/hip-hop album, and she for favorite soul/R&B female artist. Beyonce was a no-show because she was performing a show in Dublin, while Jay-Z's was announced off-air.

Other off-air awards went to sister duo Mary Mary for favorite contemporary inspirational artist, and New York-based group Aventura for favorite Latin artist.

Lopez drew gasps from the audience when she lost her balance after jumping off a dancer's back, and landed on the stage. But she quickly recovered her poise.

Other performers included Jackson's kid sister, Janet Jackson, who performed a medley of her hits; R&B singers Alicia Keys and Whitney Houston; rock band Daughtry; Colombian pop diva Shakira; and pop star Kelly Clarkson.

Nominees are determined by radio airplay and retail sales, while members of the public determine the winners through online voting. That's why Jackson got so many nominations, even though he did not release any new material.