The United States vowed to pursue every legal channel as it heaped pressure on Russia to expel fugitive US intelligence leaker Edward Snowden, who appears to have vanished in Moscow after failing to take a flight to Cuba.
The White House also hit out at China for allowing Snowden to leave his temporary refuge in Hong Kong, drawing a strong rebuke from Beijing which said Tuesday that claims it orchestrated his departure were "groundless".
Intrigue surrounding the former CIA agent, who embarrassed Washington with revelations of massive cyber-spying, escalated after he failed to appear on a flight to Havana from where he had been expected to continue to Ecuador and claim asylum.
Russia's Interfax news agency, known for its strong security contacts, confirmed he was not on Monday's Aeroflot flight and quoted an informed source as saying he was likely already out of the country.
WikiLeaks founder Julian Assange, himself holed up in Ecuador's embassy in London to avoid charges of sexual assault in Sweden, said Snowden was "safe" after leaving Hong Kong with a refugee document supplied by Ecuador.
Even as the US warned China and Russia of potential consequences over their handling of the saga, new revelations from the former National Security Agency (NSA) technician emerged in a Hong Kong daily.
Snowden told the South China Morning Post in a story published Tuesday that he joined contractor Booz Allen Hamilton, from which he stole secrets on NSA surveillance programs, specially to gain access to sensitive information and spill it to the press.
"My position with Booz Allen Hamilton granted me access to lists of machines all over the world the NSA hacked," he told the Post in an interview conducted on June 12. "That is why I accepted that position about three months ago."
The White House has dubbed Snowden a traitor to his country and warned both Russia and China that their relations with the United States could be damaged by their refusal to hand him over.
"We expect (the Russians) to look at the options available to them to expel Mr Snowden back to the United States," White House spokesman Jay Carney said, in comments echoed by Secretary of State John Kerry.
US President Barack Obama said his government was "following all the appropriate legal channels and working with various other countries to make sure that the rule of law is observed"
Carney lashed out at Beijing for letting Snowden go, despite a US arrest request which Hong Kong authorities said failed to meet legal requirements, and said its actions had eroded trust between the two nations.
"With regards to ... the Chinese government, we are just not buying that this was a technical decision by a Hong Kong immigration official," he said.
"This was a deliberate choice by the government to release a fugitive despite a valid arrest warrant, and that decision unquestionably has a negative impact on the US-China relationship."
China's foreign ministry spokeswoman Hua Chunying issued a robust defence, saying China "cannot accept" the US charges.
"It is unreasonable for the US to question Hong Kong's handling of affairs in accordance with law, and the accusation against the Chinese central government is groundless," she told a regular press briefing in Beijing.
Snowden was said by Russian officials to have spent Sunday night in a "capsule hotel" at Moscow's Sheremetyevo airport awaiting his onward connection.
Interfax quoted a source close to the matter as saying Russia was studying an extradition request from the United States for Snowden.
However, the source said Moscow does not have the right to either "detain or deport" Snowden because he has not officially crossed the Russian border.
Accompanied by WikiLeaks lawyer Sarah Harrison, he had been expected to take Aeroflot's 1005 GMT flight Monday from Moscow to Havana after airline sources confirmed he had checked in and had a seat allocated.
But in a dramatic sequence of events, the flight left the terminal with a pack of hopeful journalists on board and no sign of Snowden among the passengers.
Ecuadoran Foreign Minister Ricardo Patino confirmed that the Latin American country was considering Snowden's asylum request.
Ecuador's outspoken leftist President Rafael Correa has championed the cause of Assange and his allies, to the fury of the United States.
Snowden abandoned his high-paying intelligence contractor job in Hawaii and went to Hong Kong on May 20 to begin issuing a series of leaks on the NSA gathering of phone call logs and Internet data, triggering concern from governments around the world.