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.

"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."