Edward Snowden thanks supporters for pardon campaign

Snowden spoke via video link from Moscow, where he has been in exile since 2013.

National Security Agency leaker Edward Snowden has thanked supporters who launched a campaign for his pardon and said that for the sake of democracy, future whistleblowers must not be silenced.

Speaking by video link from Moscow, where he has been in exile since 2013, Snowden said that while the Founding Fathers created checks and balances to guard against government abuses, "whistleblowers, acting in the public interest, often at great risk to themselves, are another check on those abuses of power, especially through their collaboration with journalists".

He said whistleblowing "is democracy's safeguard of last resort, the one on which we rely when all other checks and balances have failed and the public has no idea what's going on behind closed doors".

The 33-year-old addressed a New York City news conference where advocates from the American Civil Liberties Union, Human Rights Watch and Amnesty International announced an online petition drive to urge President Barack Obama to pardon Snowden before he leaves office.

"Cases like Edward Snowden's are precisely why the presidential pardon power exists," ACLU Executive Director Anthony Romero said. "There is widespread consensus that Edward Snowden's actions catalysed an unprecedented debate about the proper limits of government surveillance, and his actions resulted in widespread reforms both in law and in technology that protect Americans and individuals across the globe."The supporters called Snowden a hero for exposing the extent of government surveillance by giving thousands of classified documents to journalists.

The Obama Administration has urged Snowden to return to the US to face trial.

Justice Department spokesman Marc Raimondi said: "It is important to remember Mr Snowden is not a whistleblower. He is accused of leaking classified information and there is no question his actions have inflicted serious harms on our national security."

Naureen Shah, Amnesty International's director of human rights for the US, brandished a photo of Snowden and said, "I think it's no exaggeration to say that this man changed the world."

Public figures supporting the request for a pardon include Wikipedia founder Jimmy Wales, philanthropist George Soros, Pentagon Papers leaker Daniel Ellsberg and writer Joyce Carol Oates.