The White House issued a blistering criticism of China on Monday over its decision to let Edward Snowden leave Hong Kong, as the whereabouts of the former National Security Agency contractor remained uncertain.
Amid deep frustration in Washington at Mr Snowden's continued success in evading U.S. authorities, the Obama administration also called on Russia to hand over Mr Snowden if he is in the country.
Jay Carney, White House spokesman, said relations between the U.S. and China would "unquestionably" be damaged as a result of Mr Snowden's departure on Sunday from Hong Kong, where he boarded a plane to Moscow.
"We are just not buying that this was a technical decision by a Hong Kong immigration official," said Mr Carney. "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 U.S.-China relationship."
(Read More: China Said to Have Made Call to Let Leaker Depart)
By leaving Hong Kong for Russia, Mr Snowden has set off a diplomatic game of cat and mouse that has left the Obama administration scrambling to find a way to bring him back to the US, where he faces espionage charges.
The 30-year-old has become America's most wanted fugitive since he leaked documents about U.S. surveillance programmes, including the mass collection of telephone data and claims about the monitoring of online communications. In an interview published in the South China Morning Post on Monday, Mr Snowden admitted that he took a job with intelligence contractor Booz Allen Hamilton to gather evidence about surveillance.
While reports said Mr Snowden was booked on a Monday flight to Cuba, he was not on the plane, according to journalists on board. He has applied to the Ecuador government for asylum, although it is still not clear if that is where he hopes to travel eventually.
(Read More: WikiLeaks' Assange Seeks Asylum at Ecuador Embassy)
Mr Carney said on Monday that the U.S. believed Mr Snowden was still in Russia. Julian Assange, the founder of WikiLeaks, which is providing Mr Snowden with legal assistance, said the NSA whistleblower was "healthy and safe" but provided no other information about his whereabouts. Mr Assange said that Mr Snowden had been provided with refugee documents of passage by the Ecuador government.
Earlier in the day, John Kerry, U.S. secretary of state, warned Russia that it should hand over Mr Snowden to US authorities. "They are on notice with respect to our desires," he said. "It would be deeply disappointing if he was wilfully allowed to board an aeroplane . . . There would be without any doubt . . . consequences."
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Over the past two years, Mr Kerry said, the U.S. government had transferred seven prisoners to Russia at Moscow's request. "Reciprocity in enforcement of the law is important," he said.
In an interview on CNN, Mr Kerry also warned that "people may die" as a result of the information that Mr Snowden leaked. "It is possible that the United States would be attacked because terrorists may now know how to protect themselves in some way or another that they didn't know before," he said.
(Read More: US Warns Countries Against Snowden Travel)
Alexei Pushkov, head of the foreign affairs committee in the lower house of the Russian parliament, said: "Ties are in a rather complicated phase and when ties are in such a phase, when one country undertakes hostile action against another, why should the United States expect restraint and understanding from Russia?"
He said, however, that there was no talk of granting asylum to Mr Snowden in Russia.
The Hong Kong authorities said there was no legal reason to prevent Mr Snowden from leaving for Russia and that they had not been informed by the US that his passport had been revoked before he travelled.
However, that position was contradicted by the White House. "I can say that the Hong Kong authorities were advised of the status of his travel documents in plenty of time to have prohibited travel as appropriate," said Mr Carney.
He said the U.S. and China had recently begun a new push to build "strategic trust". "We think that they have dealt that effort a serious setback. If we cannot count on them to honour their legal extradition obligations, then there is a problem."
Ricardo Patiño, the Ecuadorean foreign minister, said at a press conference in Vietnam on Monday that his government was "considering" the asylum request because Mr Snowden in his application said it was "improbable" he would "receive a fair trial or proper treatment before that trial" in the US.
Mr Patiño said Quito was in discussions with Moscow, "so the Russian government can make the decision that it considers most convenient in accordance with its politics and laws and in accordance with the international laws and norms that could be applied to this case".
He questioned whether Mr Snowden had committed treason against the US or only "against the elites in certain countries in the world".
"There's been talk about the word 'treason' these past few days . . . The question should be: who betrayed whom?" Mr Patiño said.
US lawmakers have claimed that Mr Snowden may be co-operating with Russia's secret services in exchange for the green light given by the Kremlin to his trip. However, Russian experts said this was unlikely.
(Read More: Snowden Rejects Suggestions He Is A Spy For China)
"There is no information about this," said Dmitry Peskov, Kremlin spokesman, when asked whether there was any contact between Mr Snowden and Russian authorities.
Andrei Soldatov, a Moscow-based expert on Russia's special services who runs the website Agentura.ru, said he doubted Mr Snowden was being asked to co-operate. "The Snowden case is much more important for politicians than it is for foreign intelligence services," he said.
He made an analogy to the case of Richard Tomlinson, an MI6 operative who published his memoirs in Russia in 2001 after a number of western countries refused to do so under pressure from the UK. "This was a strictly political matter," said Mr Soldatov. "They never tried to use Tomlinson for intelligence gathering."
"The political impact of such cases far outweighs any intelligence benefits."