Las Vegas, Apr 15 (IANS): Filmmaker James Cameron, who previously planned three sequels for his American epic science fiction film "Avatar", has announced that he and his creative team are adding another follow-up story to the franchise.

"We have decided to embark on a truly massive cinematic process. We began to bump up against the limitations for our art form," Cameron said during Fox's panel at CinemaCon here, as quoted by hollywoodreporter.com.

Cameron said as he was planning the three sequels, he found it limiting.

"We began to bump up against the limitations for our art form," he said, explaining that he decided he would need more instalments to tell the whole story.

Cameron said each of the four sequels will be able to stand alone, but will together create a saga. His goal is to release "Avatar 2" at Christmas 2018 and then a new film in 2020, 2022 and 2023.

"I've been working the last couple of years with a team of four top screenwriters to design the world of Avatar going forward: the characters, the creatures, the environment, the new cultures.

"So far, the art I'm seeing is, in pure imagination, really far beyond the first film. It's going to be a true epic saga," he added.