Pop icon Britney Spears has revealed that she has recently laid down vocals on an incredibly emotional song that is likely to feature on her upcoming new studio album.

On August 20, the superstar took to her official Twitter page and told her 30.8 million followers that working with Sia was fantastic because together they came up with something both 'beautiful and heartbreaking':

"The song is both beautiful and heartbreaking @Sia. Evokes SO much emotion every time I hear it. One of the most beautiful songs I have recorded in a LONG time :)"

Sia also posted a message on the social networking site, praising Spears for her talent: "@britneyspears your vocal on this tune is outstanding. WERK!"

Meanwhile, Spears is currently hosting a countdown site (pictured below) that alludes to the date September 17. The tagline for the countdown is 'All Eyes On Me'.