Ludacris stands on stage during a rehearsal for the Billboard Music Awards in Las Vegas, Sunday, Dec. 3, 2006. The Billboard Music Awards air live on Monday. (AP Photo/Mark J. Terrill)

LAS VEGAS - The field of chart-topping potential winners was wide open as four acts from different genres led the pack of nominees for Monday's 2006 Billboard Music Awards.

Southern rapper T.I., Canadian rockers Nickelback, country trio Rascal Flatts and R&B songstress Mary J. Blige each had five nominations. Blige was also scheduled to perform during the two-hour live show from the MGM Grand (8 p.m. EST on Fox). Among other promised performers: Janet Jackson, the Killers, Ludacris and Gwen Stefani.

The telecast would not, however, be featuring Tinseltown's duo du jour — heiress Paris Hilton and mom-gone-wild Britney Spears. After their recent binge of late-night partying, it was reported that the new best friends would be co-hosting the show, but that's not in the works.

Hilton, according to her publicist, backed out because of "objectionable" material in the script. Show producers said that Spears was never confirmed.

Crooner Tony Bennett, was to be honored with the Billboard Century Award, a lifetime achievement award.

Bennett timed his release of "Duets: An American Classic" — featuring Bono, Stevie Wonder, Paul McCartney, Barbra Streisand and other musical big-timers — to his 80th birthday. Since its September release, it has become the best-selling album of his 50-plus-year recording career.

Rock powerhouse Nickelback was up for artist of the year, as well as rock artist of the year, group and rock group of the year, and album and rock album of the year for its "All the Right Reasons."

The rockers were joined by Nashville-based Rascal Flatts in two of the categories. The multiplatinum country band also was nominated for artist of the year and group of the year, as well as a string of country nominations, including country album of the year for their fifth album, "Me and My Gang."

Mary J. Blige dominated nominations in the R&B/Hip-Hop categories. Her "The Breakthrough" won an American Music Award last month for best rhythm & blues album and was nominated in the same category Monday. The 35-year-old artist was vying with Beyonce and 18-year-old newcomer Rihanna for female artist of the year.

Blige was joined by Atlanta rapper T.I. and Jamie Foxx in the R&B/Hip-Hop artist of the year and R&B/Hip-Hop album of the year categories.

T.I. also was up for rap artist of the year along with Sean Paul and Yung Joc. His fourth solo album, "King," which debuted at No. 1 on the Billboard albums chart in March, was nominated for best rap album of the year, along with "Tha Carter II" from Lil Wayne and Eminem's "Curtain Call: The Hits."

Teen lothario Chris Brown's self-titled debut album landed the 16-year-old hip-hopper nominations for artist of the year, male artist of the year and new artist of the year.

The Billboard Awards are given to the year's chart-topping artists. Winners are determined by the magazine's year-end chart listings, which are based on record sales and airplay.