That was quick.

After nearly a week of clubbing, partying and shopping in LA with new BFF, Paris Hilton, Us has learned exclusively that Britney Spears has abruptly pulled out of co-hosting with the heiress on the Fox Billboard Music Awards, scheduled to air live on December 4.

“She pulled out,” confirms a source with Fox. “She didn’t give a reason.”

The source tells Us that Hilton is still a possible host despite losing Spears as a sidekick. Other sources confirm that as recent as this morning, agents for both Hilton and Spears were hashing out the final terms of the contract, but at 5pm today, Spears had backed out of negotiations.

“We really don’t know the reason. But we’re disappointed she backed out.” says a Fox source.

The source says the show may go on with Hilton as solo host, or it may feature comedian (and Fox sitcom star) Brad Garrett, given he’s at the top of the show producer’s wish list.

At press time, neither Hilton or Spears’ reps were available for comment.

Source

New best friends Britney Spears and Paris Hilton are taking their act onstage: The pair will co-host next week’s Billboard Music Awards in Las Vegas, a source confirms to PEOPLE.

“There are no plans for either to perform, but they will host the event together,” says a show source. “They’ll be fun onstage together.”

Among those performing will be Janet Jackson – who will open the show – Gwen Stefani, Mary J. Blige, Ludacris, and the Fray. Carrie Underwood, Carmen Electra, Dave Navarro, Vanessa Minnillo, and Katharine McPhee are among the celebs making special appearances.

Finalists are expected to be announced shortly.

The 2006 Billboard Music Awards will air live on FOX Monday at 8 p.m. ET from Las Vegas’s MGM Grand Garden Arena.

Spears, who turns 25 on Saturday, is quickly establishing Las Vegas as her second home: She’s also confirmed to host a New Year’s Eve party at Pure Nightclub, a club spokesperson confirmed to PEOPLE Tuesday.

It’s also the city where she and Hilton first forged their newfound friendship. Earlier this month, the pair met up and partied in Las Vegas, before doing more club-hopping in Los Angeles over Thanksgiving weekend.

People

Here are just some of the comments they’re leaving on her official myspace page.

you know we all have so much love for you BUT …..this whole paris lohan deal is kinda strange.
we all do silly things when we rebound.
why dump one not so great person only to replace with two more?

Britney, I would cool it if I were you. Going out once a week would be too much (when you have kids0, but may be acceptable. Going out for 10 days in a row? This is not looking good. I am SURE that you have someone reliable watching them, BUT this is not going to look good in court. I know you are young and single now, BUT you are a mom. PLEASE go home to the kids and stay there until this custody battle is over. I am telling you this because I am looking in from the outside. It is looking horrible. Britney, I would cool it if I were you. Going out once a week would be too much (when you have kids0, but may be acceptable. Going out for 10 days in a row? This is not looking good. I am SURE that you have someone reliable watching them, BUT this is not going to look good in court. I know you are young and single now, BUT you are a mom. PLEASE go home to the kids and stay there until this custody battle is over. I am telling you this because I am looking in from the outside. It is looking horrible.

It looked so ugly…wear some panties girl!

BRITNEY I REALLY DON’T CARE FOR YOU SO CALLED COMEBACK ANYMORE, I CARE FOR YOUR KIDS PLEASE BRITNEY LISTEN TO US STOP THE STUPIDITY AND TAKE CARE OF THEM YOU ARE GOING TO LOSE THEM AND I DON’T WNAT THAT, I KNOW THEY ARE YOUR ENTIRE LIFE, PLEASE DON’T LOSE THEM DO IT FOR THEM STOP BRITNEY PLEASE STOP.
WE ARE REALLY WORRIED WE WANT BRITNEY BACK WHAT THE HELL IS GOING ON WITH YOU?
PLEASE BRITNEY PLEEEEEAAAAASEEEEEEE LISTEN!!!!

yo that clam chowder shot you gave the world was crazy it looked like k-fed beat that like it was his trailerpark step son (that one is my personal favorite)

 Maybe Britney will listen to her fans?

What’s going on with her boobies?? Wow.

I know every girl has one boob that’s bigger than the other - but it looks like she’s half Pamela Anderson, half Kate Moss!

WOW…this is INSANE.  You can see, well, EVERYTHING.  And for those of you that STILL don’t believe me…well, these prove without a shadow of a doubt, the girl does not own panties.

Britney is just a trainwreck… where are her kids?? I mean she’s been on like a weeklong Paris/alcohol binge!!