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James Cameron has given fans an update about "Avatar 2", which is said to be the beginning of a trilogy of "Avatar" sequels. The director tells EW that he is still tinkering with the script, but the designs of some aspects like sets and creatures are "pretty much" done.

Cameron explains he is busy working on the script of three "Avatar" movies including "Avatar 3 and "Avatar 4". "I'm in the process of doing another pass through all three scripts right now...Just refining. That's in parallel with the design process," Cameron says. "The design process is very mature at this point. We've been designing for about a year and a half. All the characters, settings and creatures are all pretty much [done]," he adds.

Although it's not his first time working on the story taking place in the world of Pandora, Cameron says that it's not as easy as people think. It's because fans have high expectations on the sequel, considering that the first film was very impressive.

"Because you have to challenge yourself. Obviously, expectations are going to be very high on these films, especially on 'Avatar 2', to make sure it wasn't just some big fluke the first time. So we've got to deliver. I've created a nice rod for my own back, so they say," he shares.

Sam Worthington and Zoe Saldana are back to reprise their roles as Jake Sully and Neytiri. Sigourney Weaver is set to return as well, but she will play a new character this time around. Filming is planned to take place entirely in New Zealand and the movie is expected to hit U.S. theaters in 2017.

The original movie remains the top grossing film of all time with $2.8 billion. It featured a spectacular new world beyond imagination, where humans controlled half human/half alien Avatar hybrids to explore the fictional universe Pandora.