ET EXCLUSIVE: Britney Spears Reveals 'Grueling' Rehearsal Routine

ET's Mark Steines gained exclusive access to Britney Spears' top secret rehearsal in Los Angeles as the pop diva gears up for her highly anticipated Femme Fatale tour.

Britney's tour launches on June 16 in Sacramento, California but according to the music icon, the nerves haven't hit her yet.

"I'm really excited," said Britney. "I'm probably going to be extra nervous the day before. We've been working hard for, like, two months now and everything's coming together really good."

As if two months of serious dance practice wasn't enough of a workout, the Grammy winner has also been running, which explains her "rockin'" bod.

"It can be kind of [grueling], especially when you're on stage and you're on your eighth number," said Britney. "You get really winded and you're like, 'How can I do the rest of the show?' But I've been training for a while and I actually - before I come to rehearsals - I've been working out and stuff like that so I won't have that predicament."

Britney has continued her reign as one of the top-selling music artists of the decade with her well received seventh album, Femme Fatale, which was her sixth album to debut at No. 1 on the Billboard Album Chart. The tour features guest stars Nicki Minaj and Jessie.

Tickets for the Femme Fatale tour are on sale now. Click the video to find out some of Britney's must-haves while on tour.