Britney Spears' New Single 'Till The World Ends' Leaks (Listen)

Jive Records

"Looks like the cat's out of the bag…" Tweets the singer, who plans to officially release it on Ryan Seacrest's radio show Friday.

Another Britney Spears single has hit the web.

A full-length version of "Till the World Ends" was posted online. A few hours later, Spears Twittered, "Looks like the cat's out of the bag…"

She will officially release the song Friday on Ryan Seacrest's KIIS-FM radio show.

Her seventh studio album, Femme Fatale, hits stores later this month. In an interview with V magazine, she calls it her "best album I've ever made."

Earlier this week, she previewed "Seal It With a Kiss," her single by producer Dr. Luke.

She recently released the video for "Hold It Against Me."