Film director James Cameron says the next Avatar movie has been delayed by one year and will now be released in late 2017.
Cameron is working on three sequels to Avatar, which he plans to release over consecutive years.
The first had been due in late 2016.
But he says the writing process has been "very involved" and the initial target date was probably too ambitious.
Cameron was speaking in New Zealand, where he was helping to promote the local film industry with other directors, including The Hobbit's Peter Jackson.
Cameron shot the original movie in New Zealand and is planning to shoot the sequels there.
Released in 2009, Avatar became the highest-grossing film in history, with a box office take of nearly 2.8 billion US dollars (£1.85 billion). It won three Academy Awards.
Cameron said the goal was to have the scripts for the three films completed by the end of this month. He is leading a team that is writing the screenplays.
"We're writing three simultaneously. And we've done that so that everything tracks throughout the three films. We're not just going to do one and then make up another one and another one after that," he said. "And parallel with that, we're doing all the design. So we've designed all the creatures and the environments."
Cameron said he thought it was important that each film linked forward to the next one in a satisfying way but also came to a resolution so that the audience was not left hanging.
Producer Jon Landau, who is working with Cameron on the films, said the team is taking greater security precautions following the recent hack against Sony. "I will only say 'yes' but will not tell you how," he joked.
Meanwhile, Jackson said he is putting his energy into helping launch a museum to commemorate the First World War after finishing his Hobbit trilogy.
If he has any plans for future blockbusters, he is not saying.
Jackson is a First World War history buff who owns a number of planes from the era.
He said the plan for the Wellington museum is to open during April to mark the 100th anniversary of the Gallipoli battle.
He said more galleries will be opened in future years to mark other battles in which New Zealanders fought.