Jon Landau says work has started on Avatar 4

Jon Landau has revealed that work has already started on 'Avatar 4'.

The 62-year-old producer has collaborated with director James Cameron on the sci-fi franchise and says that production has already begun on the fourth movie, which is not slated for release until 2026.

Jon told Variety: "We've completed most of the first act of 'Avatar 4' and there were logistical reasons why we needed to do that. We've designed most of the whole movie for 'Avatar 4' but we haven't actually filmed all of it – just the first act."

'Avatar' broke box office records when it was released in 2009 and a long-awaited sequel, 'Avatar: The Way of Water', is set to hit cinemas in December. Jon explained that technological advances needed to be made before a sequel could come to fruition.

He told the media at the Busan International Film Festival: "We could not have delivered what people saw, five years ago, eight years ago, nine years ago. We needed the time to take it to the level that we're able to deliver to people today."

Four 'Avatar' sequels are in the pipeline and Jon revealed that each movie will introduce a new culture, while retaining those featured in previous films.

The producer, whose other credits include 'Titanic' and 'Solaris', said: "With each sequel, we're going to introduce audiences to new cultures and new biomes. We don't leave behind the cultures that we've met."

Landau discussed how inclusivity is an important part of the 'Avatar' franchise as the protagonists in 'Avatar: The Way of Water' are refugees.

He said: "As filmmakers, we have a responsibility to use our art form to challenge people to see things differently.

"And science fiction allows us the opportunity to be a metaphor for the world in which we live without preaching about it. Because if you preach, you only reach those who are already converted."