WASHINGTON – The influential New York Times hailed fugitive intelligence leaker Edward Snowden as a "whistleblower" on Thursday and threw its weight behind calls for him to be shown clemency.

The editorial was quickly seized upon by activists campaigning to persuade President Barack Obama's administration to drop its bid to prosecute the former National Security Agency contractor.

And it touched a nerve with Times readers. More than 1,200 left comments on the daily's website within hours of the item going online, and it soared to the top of its "most viewed" items of the day.

The Times, one of several newspapers around the world to have reported on US surveillance tactics based on secret files leaked by Snowden, has previously voiced support for the 30-year-old.

But editorial page editor Andrew Rosenthal said the explicit call for the administration to cut a deal with Snowden had come about just as US public and expert opinion begins to swing behind him.

"It felt like there was a real critical mass," Rosenthal told the Times' public editor Margaret Sullivan, one of many journalists who wrote follow-up columns on the mounting furor.

The Times' case, mirrored in a similar op-ed in campaigning British daily The Guardian, was that Snowden had done the United States a service by exposing the vast scope of secret digital surveillance.

Reports based on Snowden's leaked files have revealed a global dragnet run by Washington and its allies in the English-speaking world, scooping up Internet traffic and telephone call logs.

This outraged many, including some US telecoms users and foreign governments targeted in the indiscriminate sweeps, and it has touched off a political and legal debate in the United States.

While Snowden remains in Moscow, protected by temporary political asylum, US courts have begun examining the legality of the snooping and the White House has carried out an internal review.

One federal judge has already dubbed NSA snooping "almost Orwellian" and probably illegal, and Obama has promised that his review will lead to some new limits on spy agency activity.

Legally speaking, however, Snowden still faces arrest and prosecution, and could see decades in jail for treason or espionage.

The Times opposes this, arguing that he launched a national debate.

"He may have committed a crime to do so, but he has done his country a great service," the paper wrote.

The Times urged the administration to allow Snowden to return home and "face at least substantially reduced punishment."

The National Security Council declined to comment, referring AFP to previous White House statements.

Obama has said he welcomes debate about the NSA's role, but has refused to discuss the possibility of amnesty or a presidential pardon for Snowden.

In mid-December, the White House renewed its demand for the fugitive leaker to return to face trial.

US federal prosecutors have filed a criminal complaint against Snowden, charging him with espionage and theft of government property. Some lawmakers have dubbed him a traitor.

Major rights watchdogs supported the Times' call.

Human Rights Watch's executive director Kenneth Roth tweeted: "Snowden exposed major misconduct. Others filing official complaints were ignored/persecuted. He should be pardoned."

The American Civil Liberties Union said it "couldn't agree more" with the editorial.

The editorial also echoed remarks made by Rick Ledgett, an NSA official who led a task force investigating damage from the leaks.

Last month, Ledgett became the first serving national security official to suggest publicly that Snowden could cut a deal to avoid prosecution if he stops exposing US secrets.

It is not clear how many more documents taken by Snowden have still to be revealed. Journalist Glenn Greenwald, who has worked closely with him, says there are thousands more pages to come.

Some have said a plea deal for Snowden like the one suggested by the Times could allow US investigators to at least discover the size of the breach and identify compromised programs.