Avatar and Titanic filmmaker James Cameron is greeted by Sir Peter Jackson and Lady Jackson last year.

The secret is out: two of the world's biggest film directors have officially gone into business together.

Sir Peter Jackson and James Cameron established a company on March 3, however they are remaining tight-lipped on their latest Kiwi venture.

The pair are often spotted at major film industry gatherings in Wellington, and around the world, so it hasn't come as a shock that they have started a company together.

KEVIN STENT/FAIRFAX NZ Cameron's wife Suzy Amis-Cameron greets Sir Peter Jackson and Lady Jackson.

Yet, Jackson and Cameron - both highly private individuals - are refusing to share any details.

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Even after calls to officials and sources, it is still unclear why it has been set up.

ROBERT KITCHIN/STUFF Sir Peter Jackson opens the new display at the Great War Exhibition in Wellington in 2015.

The company is called PBT New Zealand, and is jointly owned by Cameron's Auckland business, T Base 2, and Jackson's Wellington business, Wingnut Films.

Wingnut Films general manager Dominic Sheehan declined to comment on the business.

"Peter and Fran look forward to commenting about this project at an appropriate time".

LUCY NICHOLSON/REUTERS Cameron paid $20 million for two large rural properties in the Wairarapa in 2010.

Cameron's US company has not yet responded to requests for comment.

Jackson and Cameron's major activities have already overlapped.

Weta Workshop - the special effects and props company part-owned by Jackson - played a major role with Cameron on Avatar, one of the highest grossing films of all time, which was nominated for best motion picture at the 2010 Oscars.

According to company records, Cameron and his wife, Susy Amis-Cameron, reside in Malibu, California, close to his LA firm Lightstorm Entertainment.

However, in 2012, Cameron paid $20 million for two large rural properties in the Wairarapa.

At the time he bought more than 1000 hectares of land, he had a view to moving there "indefinitely" with his family.

Meanwhile Jackson, who is the director of Wingnut Films and co-owner of Weta Digital, resides in Miramar, Wellington with his wife Fran Walsh.

Jackson was awarded a knighthood in 2009, following the success of his film The Lovely Bones.

In 2016, Cameron announced there would be four more Avatar sequels.

New Zealand secured the production of the upcoming Avatar films as part of a deal signed by Cameron, producer Jon Landau, Lightstorm Entertainment, Twentieth Century Fox, and the Government.

The films would be made in New Zealand and Manhattan Beach, California, with digital production work done by Weta Digital.

As part of that deal, at least $500m will be spent in New Zealand making Avatar two, three, and four, and New Zealand will host a red carpet premiere for at least one of the films.

The first one is scheduled for release in December 2018.