Former US Vice President Dick Cheney Credit:AP "It would be foolish to volunteer yourself to" possible arrest and criminal charges "if you can do more good outside of prison than in it," he said.

Mr Snowden dismissed being called a traitor by former Vice President Dick Cheney, who made the allegations in an interview this week on Fox News Sunday. Mr Cheney was echoing the comments of both Democrats and Republican leadership on Capitol Hill, including Senate Intelligence committee Chairwoman Dianne Feinstein. "Being called a traitor by Dick Cheney is the highest honour you can give an American, and the more panicked talk we hear from people like him, Feinstein ... the better off we all are," Mr Snowden said. The Guardian announced that its website was hosting an online chat with Mr Snowden, in hiding in Hong Kong, with reporter Glenn Greenwald receiving and posting his questions. The Associated Press couldn't independently verify that Mr Snowden was the man who posted 19 replies to questions. In answer to the question of whether he fled to Hong Kong because he was spying for China, Mr Snowden wrote, "Ask yourself: if I were a Chinese spy, why wouldn't I have flown directly into Beijing? I could be living in a palace petting a phoenix by now."

He added later, "I have had no contact with the Chinese government."

Mr Snowden dismissed the US government's claims that the NSA surveillance programs had helped thwart dozens of terrorist attacks in more than 20 countries, including the 2009 al-Qaeda plot by Afghan American Najibullah Zazi to blow up New York subways. "Journalists should ask a specific question: ... how many terrorist attacks were prevented SOLELY by information derived from this suspicionless surveillance that could not be gained via any other source? Then ask how many individual communications were ingested to acheive (sic) that, and ask yourself if it was worth it." He added that "Bathtub falls and police officers kill more Americans than terrorism, yet we've been asked to sacrifice our most sacred rights for fear of falling victim to it." Mr Snowden was working as a contractor for NSA at the time he had access to the then-secret programs. He defended his actions and said he considered what to reveal and what not to, saying he did not reveal any US operations against what he called legitimate military targets, but instead showed that the NSA is hacking civilian infrastructure like universities and private businesses. "These nakedly, aggressively criminal acts are wrong no matter the target. Not only that, when NSA makes a technical mistake during an exploitation operation, critical systems crash," he said, though he gave no examples of what systems have crashed or in which countries.

"Congress hasn't declared war on the countries — the majority of them are our allies — but without asking for public permission, NSA is running network operations against them that affect millions of innocent people," he said. "And for what? So we can have secret access to a computer in a country we're not even fighting?" Mr Snowden was referring to Prism, one of the programs he disclosed. The program sweeps up Internet usage data from all over the world that goes through nine major US-based Internet providers. The NSA can look at foreign usage without any warrants, and says the program doesn't target Americans. US officials say the data-gathering programs are legal and operated under secret court supervision. Mr Snowden explained his claim that from his desk, he could "wiretap" any phone call or email — a claim top intelligence officials have denied. "If an NSA, FBI, CIA, DIA, etc. analyst has access to query raw SIGINT (signals intelligence) databases, they can enter and get results for anything they want," he wrote in the answer posted on the Guardian site. "Phone number, email, user id, cell phone handset id (IMEI), and so on — it's all the same." The NSA did not immediately respond to an email seeking comment. But Director of National Intelligence James Clapper has said that the kind of data that can be accessed and who can access it is severely limited.

Mr Snowden said the restrictions on what could be seen by an individual analyst vary according to policy changes, which can happen "at any time," and said that a technical "filter" on NSA data-gathering meant to filter out US communications is "weak," such that US communications often get ingested. The former contractor also added that NSA provides Congress "with a special immunity to its surveillance," without explaining further.

Snowden defended U.S. Army Private First Class Bradley Manning for his disclosures of documents to Wikileaks, which he called a "legitimate journalistic outlet," which "carefully redacted all of their releases in accordance with a judgment of public interest." He said the Wikileaks release of unredacted material was "due to the failure of a partner journalist to control a passphrase," which led to the charge against PFC Manning that he dumped the documents, which Mr Snowden called an attempt to smear PFC Manning. PFC Manning is currently on trial at Fort Meade — the same Army base where the NSA is headquartered — on charges of aiding the enemy for releasing documents to Wikileaks. Mr Snowden defended his description of his salary as being $US200,000 ($208,800) a year, calling that a "career high," but saying he did take a pay cut to take the job at Booz Allen Hamilton, where he worked as a contractor at an NSA facility in Hawaii. When Booz Allen fired him, they said his salary was $US122,000.

Loading In one of his final replies, Mr Snowden attacked the "mainstream media" for its coverage, saying it "now seems far more interested in what I said when I was 17 or what my girlfriend looks like rather than, say, the largest program of suspicion-less surveillance in human history." AP Follow IT Pro on Twitter