Amid mounting calls to prosecute, Snowden could seek asylum in Iceland or Russia.
The United States is braced for a drawn-out effort to capture Edward Snowden, the rogue spy who dramatically exposed its domestic surveillance apparatus, as President Barack Obama was urged to prosecute him for treason.
The New York Times reported that US Justice Department officials had begun the process of charging Snowden with disclosing classified information.
Snowden, a 29-year-old intelligence contractor, was seeking asylum after apparently leaving a hotel in Hong Kong, where he leaked top secret documents on the National Security Agency (NSA) to the media.
"The only thing I can do is sit here and hope the Hong Kong government does not deport me," Snowden told the Guardian, while suggesting that he could alternatively seek protection in Iceland.
The Times in London reported that Russia will consider offering Snowden asylum. Amid calls for Snowden to face charges for treason, a Kremlin spokesman told Kommersant Moscow would give a formal asylum request serious consideration. "If we receive such a request, we will consider it," Dmitry Peskov said.
Senior US congressmen have accused Snowden of inflicting a historic blow to US intelligence and providing assistance to al-Qaeda, by disclosing the Government's telephone and online spying methods. Some former intelligence officials even accused him of being a Chinese agent.
"The United States government must prosecute him to the fullest extent of the law and begin extradition proceedings at the earliest date," said Peter King, a Republican Congressman for New York and chairman of the House homeland security committee.
John Bolton, a former US ambassador to the United Nations, accused Snowden of "the worst form of treason" and joined mounting calls to see him prosecuted under the Espionage Act of 1917.
"This man is a liar," said Bolton. "He took an oath to keep the secrets that were shared with him so he could do his job. He said he would not disclose them, and he lied."
Dianne Feinstein, chairwoman of the national intelligence committee, has ordered the NSA to review how it limits the exposure of Americans to surveillance. "What he [Snowden] did was an act of treason," she said.
But Paul Ryan, the former Republican vice-presidential nominee, raised questions about the privacy issue.
"I'm sure somebody can come up with a great computer program that says: 'We can do X, Y, and Z,' but that doesn't mean that it's right."
Jay Carney, the White House press secretary, said: "If [congressional] debate were to build to a consensus around changes [to the Patriot Act] the president would look at that. Although this is hardly the manner of discussion we hoped for, we would still like to have the debate."
The journalist who exposed the classified US surveillance programmes said that there will be more 'significant revelations' to come from the documents. "We are going to have a lot more significant revelations that have not yet been heard over the next several weeks and months," said Glenn Greenwald of the Guardian.
Snowden's disclosures also raised questions about the corporate outsourcing of US intelligence operations over the past decade. More than half the 25,000 staff of Booz Allen, his employer, hold government security clearances.
Bob Baer, a former CIA case officer, said: "The process has just been a great wealth transfer to the private sector. And I hate the systems they've built because they never caught a terrorist."
The whistleblower, who worked at Booz Allen's Hawaii office, claimed that Hong Kong had a "spirited commitment to free speech and the right of political dissent", despite continuing crackdowns in mainland China.
Experts said that he had placed himself under threat of ultimately being returned to the US by choosing to station himself in a territory that has a 17-year-old extradition treaty with Washington.
However, he could benefit greatly from Hong Kong's asylum system having been in limbo since a landmark court ruling was made there in March this year.
Its court of final appeal ruled that the Hong Kong government, which previously depended on rulings by the United Nations refugee authorities, must establish its own asylum screening process. Because no system has yet been implemented, an application from Snowden would face lengthy delays.
The Chinese Government, which has controlled Hong Kong since its return from Britain, appears entitled to veto any deportation that would affect its "defence, foreign affairs or essential public interest".
Baer said some US intelligence officials suspected Chinese involvement in Snowden's leaks and feared Beijing would thwart US attempts to capture him. Other analysts doubted that China would risk further souring relations with Washington by defying an attempt to extradite Snowden.