WASHINGTON - The former National Security Agency contractor who revealed the US government's top-secret monitoring of Americans' phone and Internet data fought back against his critics on Monday, saying the government's "litany of lies" about the programs compelled him to act.

Edward Snowden told an online forum run by Britain's Guardian newspaper that he considered it an honor to be called a traitor by people like former Vice-President Dick Cheney, and he urged President Barack Obama to "return to sanity" and roll back the surveillance effort.

A live chat of Edward Snowden, former contractor at the National Security Agency (NSA), is monitored by Tom Grundy, co-organizer of a rally that was held on Saturday supporting Snowden, on a screen at his home in Hong Kong June 17, 2013. [Photo/Agencies]

Taking questions from readers and journalists, Snowden talked about his motivations and reaction to the debate raging about the damage or virtue of the leaks. Snowden remains in hiding, reportedly in Hong Kong.

Snowden said disillusionment with Obama contributed to his decision but there was no single event that led him to leak details about the vast monitoring of Americans' activity.

"It was seeing a continuing litany of lies from senior officials to Congress - and therefore the American people - and the realization that Congress ... wholly supported the lies," said Snowden, who had worked at an NSA facility in Hawaii as an employee of contractor Booz Allen Hamilton before providing the details to the Guardian and Washington Post.

Snowden referred to Director of National Intelligence James Clapper's testimony to Congress in March that such a program did not exist, saying that seeing him "baldly lying to the public without repercussion is the evidence of a subverted democracy. The consent of the governed is not consent if it is not informed."

The Justice Department has opened a criminal investigation into Snowden's actions, and US officials promised last week to hold him accountable for the leaks.

Since Snowden went public in a video released by the Guardian on June 9, many US lawmakers have condemned his actions and intelligence officials have said the leaks will compromise national security.

Some lawmakers have been more restrained. Republican Senator Rand Paul, a Tea Party favorite, has said he is reserving judgment about Snowden's methods, and separately encouraged Americans to be part of a class-action lawsuit against the US government for the surveillance programs.    

Snowden, who traveled to Hong Kong before details of the programs were published, has promised to stay in Hong Kong and fight extradition.

China made its first substantive comments on Monday regarding Snowden's revelations. A Chinese Foreign Ministry spokeswoman said that Washington should explain its surveillance programs to the world, and she rejected a suggestion that Snowden was a spy for China.

Snowden said during the online forum on Monday that he does not believe he can get a fair trial in the United States.

"The US government, just as they did with other whistleblowers, immediately and predictably destroyed any possibility of a fair trial at home, openly declaring me guilty of treason and that the disclosure of secret, criminal and even unconstitutional acts is an unforgivable crime. That's not justice," he said.

Obama and administration officials have defended the program as an effective tool in its effort to protect Americans from terrorist attacks and said it was instrumental in helping to disrupt dozens of potential attacks.

General Keith Alexander, director of the NSA, will testify on Tuesday at a House of Representatives Intelligence Committee hearing on the programs.

Officials have promised to make public details on some of the thwarted attacks, and a US government source familiar with the matter said more than 25 cases were on a list that spy agencies were trying to declassify for Tuesday's hearing.

During his question-and-answer session with Guardian readers, Snowden rejected criticism from defenders of the surveillance programs - including Cheney - that he was a traitor for leaking the details.

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