Los Angeles, Sep 8 (IANS): Filmmaker James Cameron says the sequel of "Avatar" will be a "family saga" and will focus on human struggle.

"The storyline in the sequels really follows Jake (Sam Worthington) and Neytiri (Zoe Saldana) and their children. It's more of a family saga about the struggle with the humans," Cameron told variety.com.

Cameron promised the second film would come out in Christmas 2018, and he does not want the subsequent instalments to release too far from each other.

"We haven't moved that target yet, but we will if we need to. The important thing for me is not when the first one comes out but the cadence of the release pattern.

"I want them to be released as close together as possible. If it's an annual appointment to show up at Christmas, I want to make sure that we're able to fulfil on that promise," he added.

Production on the second "Avatar" film is expected to begin in 2017, with Stephen Lang and Sigourney Weaver returning to portray their roles from the first film as Colonel Miles Quaritch and Dr. Grace Augustine respectively. It is unclear how the two characters will be involved in the film since both of them died in the first film.

The other three instalments are scheduled to be released in 2020, 2022 and 2023 respectively.

"Avatar", which released in 2009, collected over $2.5 billion at the box office internationally.