NSA whistleblower Edward Snowden, an analyst with a US defence contractor, is seen in this still image taken from video during an interview by The Guardian in his hotel room in Hong Kong June 6, 2013. Snowden, an American who has leaked details of top-secret US surveillance programs, is technically free to leave Hong Kong at any time, local lawyers said on June 12, but the ex-CIA employee said he would stay. Snowden has not been charged by the US government nor is he the subject of an extradition request. If Washington asks for his extradition, it will be decided in court. Picture taken June 6, 2013. Photo/Agencies]

US National Security Agency whistleblower Edward Snowden, an analyst with a US defence contractor, is pictured during an interview with the Guardian in his hotel room in Hong Kong June 9, 2013. The 29-year-old contractor at the NSA revealed top secret US surveillance programs to alert the public of what is being done in their name, the Guardian newspaper reported on Sunday. Snowden, a former CIA technical assistant who was working at the super-secret NSA as an employee of defence contractor Booz Allen Hamilton, is ensconced in a hotel in Hong Kong after leaving the United States with secret documents. Photo/Agencies]

Photos of Edward Snowden, a contractor at the National Security Agency (NSA), and US President Barack Obama are printed on the front pages of local English and Chinese newspapers in Hong Kong in this illustration photo June 11, 2013. Snowden, who leaked details of top-secret US surveillance programs, dropped out of sight in Hong Kong on Monday ahead of a likely push by the US government to have him sent back to the United States to face charges. Photo/Agencies]

A statement by Hong Kong online media "In Media Hong Kong" supporting Edward Snowden, a contractor at the National Security Agency (NSA), is displayed alongside a petition to "Pardon Edward Snowden" on a White House website, on a computer screen in Hong Kong in this June 12, 2013.Photo/Agencies]

Passengers stand beside a TV screen broadcasting news of Edward Snowden, a contractor at the National Security Agency (NSA), on a train in Hong Kong June 13, 2013. Snowden, who revealed the US government's top-secret monitoring of phone and Internet data, says he intends to stay in Hong Kong and fight any effort to bring him back to the United States to face charges.Photo/Agencies]

Guardian journalist Glenn Greenwald (left), who has interviewed former CIA employee Edward Snowden, leaves the hotel where Greenwald is staying, in Hong Kong June 10, 2013. Snowden, 29, has identified himself as the person who gave the Guardian and the Washington Post classified documents about how the US National Security Agency (NSA) obtained data from US telecom and Internet companies. Snowden's decision to flee to Hong Kong as he prepared to expose the US government's secret surveillance programs may not save him from prosecution due to an extradition treaty in force since 1998. Greenwald, the lead author of the Guardian's surveillance stories, told the New York Times that he expects a US investigation and upgraded the security measures on his computer in Brazil, where he lives, as a precaution. Photo/Agencies]

Guardian journalist Glenn Greenwald, who interviewed former CIA employee Edward Snowden, leaves the hotel where Greenwald is staying, in Hong Kong June 10, 2013. Snowden, 29, has identified himself as the person who gave the Guardian and the Washington Post classified documents about how the US National Security Agency (NSA) obtained data from US telecom and Internet companies. Snowden's decision to flee to Hong Kong as he prepared to expose the US government's secret surveillance programs may not save him from prosecution due to an extradition treaty in force since 1998. Greenwald, the lead author of the Guardian's surveillance stories, told the New York Times that he expects a US investigation and upgraded the security measures on his computer in Brazil, where he lives, as a precaution. Photo/Agencies]

General Keith Alexander, commander of the US Cyber Command, director of the National Security Agency (NSA) and chief of the Central Security Service (CSS), arrives at the Senate Appropriations Committee hearing on Cybersecurity: Preparing for and Responding to the Enduring Threat, on Capitol Hill in Washington June 12, 2013. Photo/Agencies]

General Keith Alexander, commander of the US Cyber Command, director of the National Security Agency (NSA) and chief of the Central Security Service (CSS), testifies before the Senate Appropriations Committee hearing on Cybersecurity: Preparing for and Responding to the Enduring Threat, on Capitol Hill in Washington June 12, 2013.Photo/Agencies]

General Keith Alexander (left), commander of the US Cyber Command, director of the National Security Agency (NSA) and chief of the Central Security Service (CSS), testifies before the Senate Appropriations Committee hearing on Cybersecurity: Preparing for and Responding to the Enduring Threat, on Capitol Hill in Washington June 12, 2013. Photo/Agencies]

A picture shows Edward Snowden in 2002 putting a clothespin on his chest for fellow employees when he worked as a webmaster and editor for a Japanese anime company run by friends in Maryland. Photo/Agencies]

A picture shows Edward Snowden in 2002 dancing. The photograph was posted by a co-worker when he worked as a webmaster and editor for a Japanese anime company run by friends in Maryland. Photo/Agencies]

The house belonging to Lonnie and Karen Snowden, father and stepmother of NSA whistle-blower Edward Snowden, is seen in Upper Macungie Township, Pennsylvania June 11, 2013. Edward Snowden has become known worldwide as the man responsible for exposing vast surveillance programs by the National Security Agency, one of the most secretive government agencies in the United States. Photo/Agencies]

A member of the media adjusts a microphone outside the house belonging to Lonnie and Karen Snowden, father and stepmother of NSA whistle-blower Edward Snowden, in Upper Macungie Township, Pennsylvania June 11, 2013. Edward Snowden has become known worldwide as the man responsible for exposing vast surveillance programs by the National Security Agency, one of the most secretive government agencies in the United States.Photo/Agencies]

Britain's Foreign Secretary William Hague is seen making a statement to the House of Commons in this still image taken from video, in central London June 10, 2013. Britain on Monday denied claims that its security agencies had been circumventing UK law by using information gathered on British citizens by PRISM, a secret US eavesdropping program. [Photo/Agencies]