Britney Spears has definitely been toning that body of hers.

In a new tour rehearsal photo gallery posted on her official site Friday, the superstar singer works with her choreographers JaQuel Knight and Jose.

Here's Britney showing off her rock hard abs. Damn, girl ...

Maybe it's out of jealousy toward Victoria Prince, but Spears has shed as much as 20 pounds in recent months, whittling her waistline to its trimmest in years.

She credits her demanding two-hour cardio-and-strength-training workouts three times a week (on top of dance rehearsals) for the progress, reports say.

She has also been revamping her diet, opting for a 1,100- to 1,200-calorie-a-day plan consisting of three meals (think breakfast burritos, barbeque chicken salad and turkey burgers) and two snacks (such as cheese and nuts).

Britney Spears officially kicks off her big world tour, fittingly titled "The Circus Starring Britney Spears," March 3 in her home state of Louisiana.

Click to enlarge more photos of her working out with the dancers: