Vanessa Hudgens has reassured fans the entire cast of High School Musical will sign up to appear in a third installment of the teen movie.

Hudgens and co-star Ashley Tisdale have already signed contracts for Hsm 3, but Hudgens is confident all the original castmates will return for the movie - which will be the first High School Musical to have a national theatrical release - insisting, "We're all definitely on board."

She adds, "I am so very excited. To do a third one for the big screen, I can't begin to think how much fun we'll have."

Director Kenny Ortega says, "We're all verbally committed, and we're all very hopeful of doing this."

The first two movies broke TV records when they aired in America.

Shooting on the third film is scheduled to begin in January.