Sir Peter Jackson says there was a very real danger that the Hobbit movies would be made outside New Zealand.
In an interview with Radio New Zealand's Morning Report programme on Tuesday Sir Peter said that if New Zealand wants to continue producing big budget films locally, it has to keep up with incentives being offered by other countries.
Sir Peter's film The Hobbit: An Unexpected Journey - the first in the latest trilogy based on J R R Tolkien's fantasy novels - has its premiere in Wellington on Wednesday.
Two years ago, his company Wingnut Films Productions and the New Zealand Actors' Equity union were at loggerheads over a collective pay agreement.
Sir Peter said the dispute created the very real danger the films would have been made in the United Kingdom and the threat was not brinksmanship by Warner Bros, which sent proof it was looking elsewhere.
The worst time for him was when a huge box arrived at his office from the studio.
"They had sent a location scout around England and Scotland to take photos, and they literally had the script broken down into each scene.
"In each scene there were pictures of the Scottish Highlands and forests in England and this and that - and it was to convince us that we could easily just go over there and shoot the film."
Sir Peter says he doesn't know whether Warner Bros aimed to get more taxpayers' money for the films when executives flew to New Zealand during the dispute in 2010.
But he says he knows there is no room for sentimentality when studios decide where big budget films will be made, and if New Zealand wants to be in the business of making films it has to be aware of what other countries and US states are offering up as tax incentives.
Sir Peter said he would be tweaking the sound track and making improvements on The Hobbit: An Unexpected Journey until the last moment before its premiere.
Asked at what point he would have to step back and accept it was finished he said: "When they rip it out of your hands."
"I'm going to be happy if people like it - and at this point in time it's a little bit too early to say. You lose objectivity - that's the thing with a movie that's the most scary. You realise when you're deep in the process that you've no idea whether it's good or bad."
As for the rest of the trilogy, filming will continue for the final Hobbit film for another 10 or 12 weeks early next year.
The director praised the New Zealand crews working on the films for their enthusiasm and ingenuity.
"If you need to put something together at the last minute out of stuff that you've got lying around, there's no-one better than the New Zealand art department to get that set built."
Sir Peter says the Hobbit movies will probably be the last of his ventures in Middle Earth.