Robert Pattinson says he's struggling to come to terms with the success of The Twilight Saga.

The 23-year-old actor, who plays vampire Edward Cullen, admitted he only agreed to do the franchise so he could work on a US film.

"It worries me, because the whole Twilight thing keeps getting bigger and bigger, and now it's so big, even my own ego can't cope with it,” Pattinson told Times Live.

“A certain amount of success you can mentally deal with, but there's a point where you think: 'Jesus Christ, what is this? I'm not that great!'”

He added: “I just wanted to make an American film, and I wanted it to be relatively good and to be good in it. I have never pushed to do anything.”

Pattinson, who is currently promoting the second installment of the saga, New Moon, also claimed it was easier to get breaks as an English actor.

“You're allowed to look a little worse. It's that thing about English teeth,” he said.

New Moon is on general release in cinemas now.

Robert Pattinson