A lone hero is on the run, eluding a spy-hunt across a globe-trotting storyboard as he strives to expose wrongdoing at the heart of Washington's vengeful intelligence apparatus.

The script's ending is not yet written but that, for his supporters at least, is the Jason Bourne-style narrative of Edward Snowden. For them, the former National Security Agency (NSA) contractor's exposure of a many-tentacled eavesdropping campaign represents the made-for-Hollywood stand of one man fighting impossible odds.

For the US government, the leaks made by the 30-year-old IT specialist risk allowing extremists to plot and maim unhindered.

While Snowden has won sympathy internationally, Washington has cast him at best as a misguided fool, at worst as a traitorous villain in the pay of hostile powers.

Whatever the validity of his actions, the scene-shifting drama has made for a riveting spectacle that observers believe will eventually end up on the big screen.

The plot at times has strained credulity, but it is all real, starting with Snowden's decision in May to abandon his pole-dancing girlfriend in Hawaii for Hong Kong and a life on the run.

"Every spy novelist in the world is not writing at the moment, because they are glued to this -- it is the biggest spy case there has been in decades," Jeremy Duns, the author of three novels about a turncoat British agent in the Cold War, told AFP.

Like other observers, Duns expects a movie or book tie-in before long to explore the nuances of a story that seems ripped from the pages of John le Carre, dwelling on themes of moral ambiguity, conflicted loyalties and outright betrayal.

Any adaptation of the Snowden saga will have to give prominent billing to the NSA, an organisation so secretive that it was once dubbed "No Such Agency".

The NSA emerged from the shadows in the 1998 film "Enemy of the State", featuring Will Smith and Gene Hackman.

Well before the 9/11 attacks, it covered the encroaching reach of the surveillance machine - one that in the movie's telling would stop at nothing, not even murder, to expand its powers and shield its secrets.

In comments dismissed by his critics as paranoid ravings, Snowden on June 17 evoked the threat of the US government "murdering me", but said his stream of revelations could not be dammed.

"Truth is coming, and it cannot be stopped," he told Guardian readers, in what could pass for the tag line of a Hollywood film.

Snowden has injected a twist into the traditional plot. The unglamorous IT guy, munching on pizza as he beavers away at his laptop, is now the leading man.

"The geek in the van has become the Bourne," said Duns, who has also written a history of the 1960s Soviet spy Oleg Penkovsky published this month.

-- 'A very modern American story' --

In fact, according to the Hollywood trade press, A-list director Michael Mann is working on a project tentatively called "Cyber" that will portray the US and Chinese militaries coming together to thwart a dangerous hacking conspiracy. Mann has been scouting locations in Hong Kong.

The Chinese territory was the setting for a month-long stay by Snowden that took in endless room-service meals at a boutique hotel in bustling Kowloon before he decamped in the dead of night to the homes of local supporters.

Filmic touches included a dinner of pizza and Pepsi with his lawyers at which Snowden insisted that all present stash their mobile phones in the fridge to block any signals.

Invoking James Bond's drink of choice, one expert cited by the New York Times said the insulating properties of a fridge are shared by a martini shaker.

Any film that wants to stay true to Snowden's international odyssey will need a hefty budget to cover location shoots, from Hawaii to Hong Kong, onwards to Russia and then elsewhere, via stops in Washington and Beijing to cover the back-story of top-level intrigue.

Like Tom Hanks in "The Terminal", Snowden now finds himself in airport limbo, seemingly stuck in Moscow as he ponders his next move -- possibly asylum in Latin America.

In one scene straight from a spy thriller, the fugitive threw his pursuers off the trail by booking to take one flight from Moscow to Cuba, only to fail to show up.

Frustrated journalists who did take the Aeroflot flight were reduced to filming the empty seat at 17A, enduring the sniggers of the crew - and an alcohol ban in economy class -- before landing 12 hours later in Havana, where the flight's captain was filmed laughing uproariously.

"I have a feeling that we are all participating in some grandiose spy conspiracy," said Olga Denisova, a journalist with Voice of Russia radio.

The supporting cast could do nothing but take refuge in dark humour. But for one major protagonist, there is nothing funny about this drama.

White House aides disdain heroic characterisations of Snowden, saying his revelations have jeopardised surveillance operations designed to keep the public safe from harm.

One US administration source bitterly rejected any comparisons between Snowden and Vietnam War leaker Daniel Ellsberg, whose life story was made into the 2003 film "The Pentagon Papers".

While Ellsberg stayed and fought in US courts, the source mocked Snowden's willingness to stand up for what he believes "from Hong Kong!"

"The story has lots of potential for dramatic adaptation, perhaps because the 'good' and 'bad' elements of the leading character are so ambiguous," commented professor Robert Thompson, a scholar of popular culture at Syracuse University in upstate New York.

"I imagine any movie adaptation will use this ambiguity and portray Snowden as neither a hero nor a villain," he said. "It's a very modern American story."

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