The movie is based on a novel by author Max Brooks.
The 49-year-old actor said there is still plenty of material to use from the book but it can only be done if the debut film is a success, reports contactmusic.com.
"It's set up for many sequels because the book is so dense with information and historical references, and it's an international story," Nuts magazine quoted Pitt as saying.
"There are so many things we could do with this - if it works. But we need this one to work - which we think it does," Pitt added. Pitt played the lead character Gerry Lane in the film and has also co-produced it.