The pop princess - who was slated for miming her way through 'comeback' performances in Europe and the US - is expected to deliver a polished live act when her world tour comes around in March 2009.
A source close to Britney said, "Britney has been told that if she doesn't deliver on this tour a lot of the public support she has earned is going to fade away.
"Britney is feeling the pressure more and more as she rehearses for the tour."
The source added, "She knows one slip-up and it could all be over for her because she will be crucified in the press.
"After what she's been through, it's hard to imagine how she's going to cope."
Source: entertainmentwise.com
