Reeling from the sensational revelation of its secret global internet monitoring programme, Washington prepared to take action against the young private contractor who leaked the details.
Edward Snowden, a 29-year-old technology expert working for a private firm subcontracted to the US National Security Agency, has become an instant hero for transparency advocates and libertarians around the globe.
But his exposure of the NSA's worldwide monitoring of private users' web traffic and of US citizens' phone records has infuriated US intelligence officials and embarrassed President Barack Obama's White House.
Snowden is thought to be holed up in Hong Kong, which has an extradition treaty with the United States, and he is cooperating with the British-based Guardian newspaper, which revealed his identity at his own request.
"The extradition agreement with Hong Kong was signed in 1996 and entered into force in 1998.
It is still in force, and we've actively used it over the years," State Department spokeswoman Jen Psaki said.
Officials refused to be drawn on whether Washington plans to demand Snowden's extradition.
But Obama's spy chief, Director of National Intelligence James Clapper, has described the leak as gravely damaging to US security, and referred the matter to the Justice Department, which has launched an investigation.
The White House declined to comment on the case, citing the ongoing probe.
But a spokesman confirmed that Clapper will carry out an assessment of the damage allegedly wrought by the leaks, and confirmed that Obama had been briefed by senior staff over the weekend about the revelations.
Snowden also told the Guardian he hopes to win asylum in Iceland, but the head of Iceland's Directorate of Immigration said it had received no formal request and said Snowden would have to be on Icelandic soil to make one.
There was much speculation about Hong Kong's likely stance in the event Washington asks for Snowden's extradition, and analysts divided on whether the territory's ultimate rulers in Beijing would intervene.
The case has also turned the spotlight on the United States' widespread use of outside contractors for sensitive intelligence work; Snowden is a former low-level CIA employee now employed by private outfit Booz Allen Hamilton.
Companies like Booz employ tens of thousands of technicians and analysts with top secret security clearances to work on lucrative contracts with US intelligence agencies, and some are asking if they pose a security risk.
Snowden and his many supporters, who have taken to the internet to condemn the US government and the private web giants which cooperated with its secret surveillance, defended his actions, saying he had struck a blow for freedom.
"My sole motive is to inform the public as to that which is done in their name and that which is done against them," Snowden said, in a Guardian video.
He said he had gone public because he could not "allow the US government to destroy privacy, internet freedom and basic liberties for people around the world with this massive surveillance machine they're secretly building."
Snowden flew to Hong Kong on May 20 after copying at the NSA's office in Hawaii the documents he intended to disclose, the Guardian said.
The US consulate in Hong Kong and the Hong Kong security bureau refused to comment on the case, but a senior pro-Beijing lawmaker in Hong Kong told reporters Snowden should probably leave the city.
Hong Kong, a special administrative region of China, is "obliged to comply with the terms of agreements" with the US government, Regina Ip said.
In a statement responding to Snowden's decision to go public yesterday, Clapper said the matter had been referred to the Department of Justice.
"The intelligence community is currently reviewing the damage that has been done by these recent disclosures," Clapper said. The Justice Department confirmed that it was investigating the matter.
Under the PRISM program, revealed by Snowden, the NSA can issue directives to internet firms like Google or Facebook to win access to emails, online chats, pictures, files, videos and more, uploaded by foreign users.
The service providers deny they have given the government backdoor access to customer data, insisting they did so only when compelled by law.
Clapper said the NSA applies to a secret court set up under the Foreign Intelligence Surveillance Act for permission to target individuals or entities and then issues a request to the service provider.
Today, rights watchdog the American Civil Liberties Union filed a motion with the FISA court demanding it publish its findings as to the scope and constitutionality of its powers to trawl internet and phone records.
"The government appears to have secretly given itself shockingly broad surveillance powers," ACLU staff attorney Alexander Abdo said.