Britney Spears has unveiled a sneak preview of 'I Am Britney Jean'.

The 'Work Bitch' singer teased fans on Twitter before posting a link to a short 30 second clip on Friday (12.12.13), in which her crew members reveal she has been under ''pressure'' in the lead up to her residency in Las Vegas which launches later this month.

The 32-year-old singer is seen performing a series of complicated dance routines before a crew member explains: ''There is a lot more people watching which creates a lot more pressure for her.

''I'm actually worried about whether the show is going to be ready.''

At one point the Britney even fears for her own health as she talks of suffering a painful injury to her neck when rehearsing complicated dance routines.

She recalls: ''I couldn't do rehearsals the next day I just knew I'd broke my neck or something, there was serious damage.''

Britney will complete a two-year residency at Planet Hollywood Resort and Casino Las Vegas, and despite the gruelling preparations she admits feeling nervous about her performance.

She adds: ''I'm really nervous, what if I just blank out and just stand there?''

'I Am Britney Jean' is to premiere on E! on December 22.