New York // The US justice department is preparing to file criminal charges against the former government contractor who confessed to leaking details of secret surveillance programmes, according to officials.
As the justice department worked on its charges against Edward Snowden, 29, the debate over the National Security Agency's collecting of vast amounts of online and phone data intensified.
Authorities in the US hope begin the process of extradition as quickly as possible, the two unnamed law enforcement officials told ABC News yesterday.
The officials spoke a day after Glen Greenwald, one of the journalists involved in breaking a series of stories based on Mr Snowden's leaks that have shaken Washington, said that there are more revelations to come.
"There are extremely invasive spying programs that the public still does not know about that the NSA regularly engages in or other capabilities that they're developing," Greenwald told CNN.
"We are working on stories right at this moment that we think are very valuable for the public to know that don't in any way harm national security but that shine a light on this extremely secretive though momentous agency," he said.
It was unclear under which law Mr Snowden might be charged but analysts said that the charges were unlikey to fall under espionage legislation because he disclosed the documents to the media rather than a foreign government.
But that did not stop senior Republican John Boehner from calling Mr Snowden a "traitor" yesterday.
A senior intelligence official told the Associated Press that Mr Snowden could be prosecuted for violating the non-disclosure agreement he would have had to have signed to gain access to classified information. The penalties range from a few years in prison to a life sentence.
Federal investigators also believe that Mr Snowden may not have been acting alone. "The FBI is not 100 per cent focused on this one guy," a senior law enforcement official told ABC. "Agents are not just guided by what he claims."
But other former intelligence officials told media outlets that the extenstive post-9/11 national security system, and its focus on digital data, means that even a relatively low-ranking computer specialist could have access to massive amounts of secret information.
With Mr Snowden, who was last seen in Hong Kong, facing the possibility of extradition to the US to face charges, transparency advocates said on Monday that they were starting a campaign to raise funds to defray his legal costs.
The former employee of defence contractor Booz Allen Hamilton has not been seen since he checked out of a hotel in Hong Kong on Monday and is apparently hiding on the island. Mr Snowden said he fled to the semi-autonomous Chinese city because of its history of supporting free speech.
But legal experts doubted whether the Hong Kong chief executive would deny an extradition request once charges have been filed, pointing to the city's long-standing relationship with the US and its history of accepting such requests.
If Mr Snowden is still in Hong Kong and is arrested by Interpol pending the extradition, the process - including appeals - could take up to a year, Michael Blanchflower, a Hong Kong lawyer and expert on extradition cases, told Associated Press.
Until charges have been filed and Interpol alerted, however, Mr Snowden would be free to travel to a nearby country that has no extradition treaty with the US, such as China. Beijing may be tempted by the sensitive intelligence it could glean from Mr Snowden, but analysts doubted whether the risk to its relationship with the US would be worth it. Mr Snowden has also shown no signs of interest in co-operating with foreign intelligence services.
In Washington, the furore around the disclosure of the NSA's efforts to track and collect data from online and phone communications grew louder.
A bipartisan group of senators led by Jeff Merkley, a Democrat from Oregon, were set to introduce legislation yesterday that would force the Obama administration to reveal the opinions of the secret court that rules on eavesdropping requests, to ascertain how it interprets the laws that the programmes rely upon.
The first document leaked by Mr Snowden was an order by one of these secret judges, which showed that one major carrier, Verizon, was forced to give the government all metadata on all phone calls made on its system over a three-month period.
Also yesterday in a closed hearing, top federal law enforcement and intelligence officials briefed House legislators on the surveillance programmes.
Legislators also said they would review ways to conduct national security without violating constitutional rights to privacy.
"There's very little trust in the government, and that's for good reason," said Representative Adam Schiff of California, who sits on the House Intelligence Committee. "We're our own worst enemy."
White House spokesman Jay Carney said President Barack Obama was open for a discussion about the spy programmes, both with allies abroad and in Congress. Apart from the justice department criminal investigation, the White House has also launched an internal review to assess the damage to its national security efforts caused by Mr Snowden's leaks, a senior intelligence official told Reuters.
A former US official told Reuters that the likely focus of such a review would be whether the disclosures had exposed sources and methods, and if those who have cooperated with US intelligence efforts have lost their willingness to continue.
Meanwhile, the European Parliament is planning to debate on the US spying programmes today and establish if they violated local privacy laws. EU officials said they would seek answers from their US counterparts at a trans-Atlantic ministerial meeting in Dublin later this week.