The former intelligence analyst who leaked details of a massive United States government surveillance operation has been charged with espionage, theft and "conversion of government property".
Edward Snowden gave thousands of documents to the Washington Post and Guardian newspapers, saying he felt he needed to expose how the United States government was violating Americans' privacy.
Calling himself Verax - Latin for "speaking the truth", in his exchanges with The Washington Post, Mr Snowden had fled to Hong Kong before leaking the details, but his current whereabouts are unknown.
The 30-year-old former American National Security Agency (NSA) contractor leaked details of a massive electronic surveillance operation showing that US agencies had systematically gathered vast amounts of phone and web data.
US officials are understood to have asked Hong Kong authorities to detain him if he is still there but Washington journalist Sari Horwitz says that could be difficult, the BBC reports.
"What experts say about this is that it's 90 percent politics and diplomacy and 10 percent law."
She says Mr Snowden could fight the effort to extradite him in the courts and the battle could take many, many months.
Although the US has an extradition treaty with Hong Kong it has an exception for political offences, she says.
The company that processed Mr Snowden's security clearance is also under investigation.
Meanwhile, a businessman from Iceland has offered to fly Mr Snowden to his country if Iceland offers him asylum.
Papers show NSA policies allow spying
Meanwhile, newly disclosed papers show America's National Security Agency does have policies allowing it to review the content of emails and phone calls made by Americans if they are considered to contain significant foreign intelligence.
US President Barack Obama has said the agency does not do those things unless a criminal investigation is underway.
