Oliver Stone tells the story of the most wanted man in the world, Edward Snowden.

Australian mogul James Packer pulled out of financing a hotly anticipated biopic about whistleblower Edward Snowden because he feared he would be denied entry to the US, legendary Hollywood director Oliver Stone says.

Appearing on a discussion panel with Foxcatcher director Bennett Miller, Stone detailed the enormous financial challenges that almost derailed his latest movie, Snowden, which he said was turned down by every major studio.

"We got turned down with a good script, a good cast and a reasonable budget at every major studio," Stone said during the weekend Q&A, which was part of the Nantucket Film Festival.

Dinuka Liyanawatte James Packer's planned $2 billion hotel casino in Sydney will proceed.

"Studio heads said, 'Yes we like it. We'll talk about it. There's no problem here.' It goes upstairs, and a few days later, nothing comes back."

Stone said the movie, which stars Joseph Gordon-Levitt as Snowden, was a "nightmare movie to finance".

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SMH Oliver Stone, pictured in Sydney in May 2015, said his upcoming movie Snowden was turned down by every major studio.

He named Packer as among those who had been interested in the project but he said that Packer ultimately pulled out for fear the movie's politically controversial subject nature would have personal consequences for him.

"He was warned by an Israeli friend of his that he wouldn't get a visa to go the United States," Stone said, US entertainment magazine Variety reported.

Reuters NSA whistleblower Edward Snowden.

"There's all kinds of things behind the scenes. It's an ugly business that way."

Miller said he had spoken to the Australian billionaire, who he said was "humiliated, embarrassed and apologetic that he had to deliver the news" to Stone that he could not help finance the film.

Ratpac Entertainment, which Packer co-founded with director Brett Ratner in 2012, has financed a swath of star-studded blockbusters, including the The Revenant, Mad Max: Fury Road and The Suicide Squad.

oseph Gordon-Levitt will play Edward Snowden in an upcoming film.

Stone revealed the movie's financial struggles had taken a toll on him, adding that production was ultimately moved to Germany where there was less hostility to the film.

"We were turned down by every studio; that's not easy for me. Every studio. We were financed out of France and Germany. A small North American distributor that did Spotlight last year, Open Road, came in with us. It's a journey, it's been a long one," Stone said.

The biographical political thriller details the life of Snowden, who leaked thousands of documents of classified information from the National Security Agency to journalists Glenn Greenwald, Laura Poitras and Ewen MacAskill in 2013, before seeking political asylum in Russia.

Snowden is slated for released in September this year.