Britney's single "leaks," some predict a club hit

The second single from Britney Spears' upcoming album "Femme Fatale" was posted on the internet on Thursday, and the upbeat dance anthem "Till the World Ends" has some pundits predicting a club hit.

Tracks leaking online has long been a problem for musicians seeking to control the release of their records, although Spears quickly took to Twitter to promote the "formal premiere" of the track on Ryan Seacrest's radio show on Friday.

Her record label also brought forward the single's digital release, making it available on iTunes on Friday, several days earlier than originally planned.

Britney has announced the full track listing for Femme Fatale, which goes on sale on March 29 and will test the public's appetite for the latest Spears comeback.

The new album will feature 12 tracks, with four extra songs available on the deluxe edition.

"I think 'Femme Fatale' speaks for itself ... I wanted to make a fierce dance record where each song makes you want to get up and move," Spears said.

Early reaction to Till the World Ends, written by fellow popstar Ke$ha and produced by Dr. Luke and Max Martin, suggests that the 29-year-old's rollercoaster career is on the up again.

"Like its predecessor 'Hold It Against Me', Spears's main intention with her new single seems to be keeping the dance floor pulsating with sweaty bodies," wrote Gerrick D. Kennedy on the L.A. Times music blog "Pop & Hiss."

"And we don't blame her, as the catchy song does make you want to grab some glow sticks and hit the clubs."

Music channel MTV opined: "Britney Spears' new single ... sounds poised to be a club smash."

The electro-pop song's message is predictably simple, summed up in the refrain: "Keep on dancin' till the world ends."

And while critics agree that it could be the work of any number of pop stars, some say Spears, whose torrid personal life has often overshadowed her musical success, has the confidence and "breathy" vocals to pull it off.

The first track from the album, "Hold It Against Me," debuted atop the Billboard Hot 100 chart in January, breaking digital download records on the way.