Washington pressed Moscow on Monday to do all in its power to expel former U.S. spy agency contractor Edward Snowden before he gets the chance to take an expected flight to Cuba to evade prosecution in the United States for espionage.

Snowden, whose exposure of secret U.S. government surveillance raised questions about Washington's intrusion into private lives, was allowed to leave Hong Kong on Sunday after Washington had asked the Chinese territory to arrest him.

His decision to fly to Russia, which like China challenges U.S. dominance of global diplomacy, is another embarrassment to President Barack Obama who has tried to "reset" ties with Moscow and build a partnership with Beijing.

The White House said it expected the Russian government to send Snowden back to the United States and lodged "strong objections" to Hong Kong and China for letting him go.

"We expect the Russian government to look at all options available to expel Mr Snowden back to the U.S. to face justice for the crimes with which he is charged," said Caitlin Hayden, spokeswoman for the National Security Council.

The Kremlin and the Russian government did not immediately comment. But Russian officials were defiant, saying Moscow had no obligation to cooperate with Washington after it passed the so-called Magnitsky law, which can impose a visa ban and asset freeze on Russian officials accused of human rights violations.

"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?" said Alexei Pushkov, the head of the foreign affairs committee in the lower house of parliament.

{reuters}