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.