Toronto (Canada) (AFP) - Patriot, dissident or traitor? A new film by anti-establishment director Oliver Stone starring Joseph Gordon-Levitt as NSA whistleblower Edward Snowden asks audiences to weigh in.

Stone -- who has unveiled his espionage thriller biopic about the largest data leak in US history at the Toronto film festival -- called Saturday on US President Barack Obama to pardon Snowden before the end of his term.

"Mr. Obama could pardon him and we hope so," Stone told reporters at the festival, the largest in North America and a launch pad for Oscar contenders.

"We hope that Mr. Obama has a stroke of lightning and he sees the way, despite the fact that he's prosecuted vigorously eight whistleblowers under the Espionage Act, which is an all-time record in American history, (and he's created) the most extensive invasive surveillance state that ever existed."

Snowden himself has said he is prepared to face prosecution in the United States, but only if the trial is public and fair.

"He would like to come home," Gordon-Levitt said, recalling encounters with Snowden in Russia where Snowden was granted political asylum after fleeing the United States.

Defending one of the world's most wanted men, Gordon-Levitt said Snowden has shown two kinds of patriotism: enlisting in the army in 2004 at the height of the Iraq war to fight for his country, and seeking to hold his government accountable via the leak.

"He really was doing what he did out of a sincere love for his country and the principles that the country was founded on," he said.

- Homesick -

Snowden's residency permit in Russia runs out next year.

"Then the question comes up again of where he can be safe. Obviously he'd love to go back home," WikiLeaks representative Sarah Harrison told AFP ahead of the film's red carpet premiere Friday in Toronto.

Alternatively, "he'd really like asylum in a number of other countries, some European countries. Maybe the situation will have changed in some of those but sadly so far he's always been denied," said Harrison, who is also the director of the Courage Foundation, which supports Snowden and other whistleblowers.

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"In this current environment in which it's kind of an empire that the US is running, his chances are minimal," she said.

Harrison opined that whistleblower protections in the United States are too weak, but that "public awareness is improving and that's always a first step."

"These sorts of actions should be protected in some way or at least be allowed a defense."

"What will help Snowden's situation and potential other whistleblowers as well is getting more public awareness of the retaliation that's used against people that do these sorts of things," Harrison said.

US authorities charged Snowden with espionage and theft of state secrets after he released thousands of classified National Security Agency documents to journalists Glenn Greenwald, Laura Poitras and Ewen MacAskill in 2013.

Considered a traitor by some and a hero by others, the 33-year-old fled to Hong Kong, where he hid among Sri Lankan refugees in cramped tenements, and later was given political asylum in Russia after the US revoked his passport.

He now leads a reclusive life there.

- 'World's most wanted dissident' -

In an encrypted text this week to Canada's daily National Post, which revealed how he had evaded US authorities while on the run, Snowden described himself as "the world's most wanted dissident."

He also expressed concern for people affected by his actions, saying "I was worried about accidentally dragging people down with me."

The documents he leaked revealed the extent of the NSA's global surveillance programs and started a debate about privacy and the role of state security agencies which still rages today.

The film is based on "The Snowden Files," a chronicle of the affair by Luke Harding of Britain's Guardian newspaper, and on the political thriller "The Time of the Octopus" penned by Snowden's Russian lawyer, Anatoly Kucherena.

It follows Snowden from the army to the CIA and to his post as an NSA analyst, delving deeper with each film frame into the big reveal: the world is teeming with electronic devices, each of them capable of monitoring our activities.

(Adhesive bandages to cover computer and smartphone cameras were handed out at the premiere).

It also stars Shailene Woodley, Melissa Leo, Zachary Quinto, Tom Wilkinson (also appearing at the festival in "Denial") and Nicolas Cage.

Working on the film made each actor more aware of their privacy rights and hacking risks, they said.

Quinto described feeling uneasy about advertisers tracking his online activities while shopping recently for a washer and dryer.

Woodley said there's a big difference between voluntarily sharing personal information on social media and having private details revealed by a hack.

"Empowerment comes from awareness," she said.