By Mike Collett-White

LONDON – The surprise success of "Twilight," the teen vampire movie that boasted a bigger opening North American weekend box office than the new James Bond, could make the sequel harder to sell, its leading actors said.

The movie, based on the bestselling novel by US author Stephenie Meyer, made $69.6 million in movie theaters over its first weekend last month, ahead of Bond film "Quantum of Solace" which cost over five times as much to make.

The success helped convince independent studio Summit Entertainment to go ahead with sequel "New Moon" based on the second book in the series, and the two lead actors from "Twilight" are down to reprise their roles.

"We had nothing to lose in the first one," said British actor Robert Pattinson, who has become a movie heartthrob virtually overnight for his portrayal of the immortal vampire Edward Cullen.

"It’s harder to build up the hype, especially in America. I think it will be harder," he told a recent London briefing. The film opens in Britain on Friday.

Kristen Stewart plays Bella Swan, the teen girl who falls in love with Cullen only to see her relationship and family jeopardized by rival vampires’ lust for blood.

Stewart said she expected the press to be "a little tougher" next time around, and had been surprised at how big the movie became in the United States.

"I knew how important it was to a small group of people. I didn’t realize how widespread they (the books) were," she said.

"I think the film made it more well-known. When we were making the movie we thought it was kind of a cult film."

Shooting on "New Moon" starts in the new year, but "Twilight" director Catherine Hardwicke will not be at the helm again despite setting a record North American box office opening for a female director.

According to Hollywood Reporter, taking her place will be Chris Weitz whose last film was "The Golden Compass," an adaptation of British author Philip Pullman’s children’s book.

For 18-year-old Stewart, playing as many different roles as possible was one way of avoiding the risk of being typecast.

"There’s a large group of people that will always consider us as these characters (but) I just did this movie called ‘Welcome to the Rileys’ which couldn’t have been more different.

"If it was just ‘Twilight’ for the rest of my life as an actor I would be quite miserable."

Pattinson said he was struggling to get used to life as a major star. The 22-year-old, who played a smaller role in the "Harry Potter" movie franchise, has been faced with crowds of screaming girls whenever he hits the red carpets for "Twilight."

"I don’t know why, I’m not getting used to it," he said. "People are screaming. I’m completely overwhelmed by it every single time.