The studio executive told Empire that James Cameron's follow-up is unlikely to make its tentative 2014 release date, but confirmed that special effects work has commenced at WETA.
"We're not naming dates, but I think 2014 will be a tough date for us to make. It's about getting it right," he said. "Movies make release dates; release dates don't make movies."
Avatar 2 will be based around the oceans of Pandora, Cameron previously revealed. Landau went on to say that his team has already begun working on underwater performance capture.
"We've started already," he added. "WETA are already working and we have our core team, [animation supervisor] Richie Baneham and [digital effects supervisor] Nolan Murtha, working with us. And we're working on underwater performance-capture.
"It's going to be like the Floating Mountains in the first movie. It's not going to be all underwater; it's going to be a place we go to, leave and come back to."
Avatar 2 is expected to be released in 2015 at the earliest.
> Sam Worthington: 'Avatar 2 plot is monumental'
Watch Avatar actor Sam Worthington discuss the sequel with Digital Spy below: