Taylor Swift and Zayn Malik have released a surprise duet.

The 'Bad Blood' hitmaker has teamed up with the former One Direction hunk on 'I Don't Wanna Live Forever', which is taken from the 'Fifty Shades Darker' soundtrack and is the 26-year-old singer's first new music this year.

Taylor shared the artwork and a clip of the track on her social media accounts before it unexpectedly appeared in the US iTunes Store late on Thursday (08.12.16) night.

The description of the track on iTunes says it features ''two of pop's brightest stars [teaming up] for a passionate duet''.

'I Don't Wanna Live Forever' is already top of the iTunes chart.

Taylor took a screengrab of the figures and wrote on instagram: ''Well that escalated quickly.''

The mid-tempo song sees Taylor and Zayn taking turns to deliver lines including, ''Baby, baby, I feel crazy/Up all night, all night and every day/Give me something, oh, but you say nothing/What is happening tonight?'' and ''I don't wanna live forever/'Cause I know I'll be living in pain/I don't want to fit wherever, I just want to keep calling your name/'Til you come back home.''

The 'Shake It Off' singer - who previously dated Zayn's former bandmate Harry Styles and is close friends with her collaborator's girlfriend Gigi Hadid - teamed up with Sam Dew and Jack Antonoff to write the song, and the track came together in just a week.

Jack revealed on Twitter: ''i don't wanna live forever came together very quickly. wrote it with taylor and sam dew and produced it at home mostly on paper sounds

''recorded taylor at my house. zayn sent parts from LA - we did it in a week basically. i've never had something come out that quick.(sic)''

It is not yet known when the song will be released outside of the US.