MOSCOW (AFP) - Russia on Friday accused the United States of putting it in a "tough spot", claiming Washington never disclosed that it had revoked the travel passport of fugitive US intelligence leaker Edward Snowden.

The former National Security Agency (NSA) contractor spent Friday holed up in a Moscow airport for a sixth day after arriving by a regular Aeroflot flight from Hong Kong where he had disclosed US surveillance secrets to the press.

A Russian official close to the matter on Friday accused the United States of apparently deliberately putting Moscow in a difficult position by never reporting that Snowden's passport had been revoked, Interfax reported.

The official said Moscow might not have allowed Snowden to fly to Russia had it known about his travel problems.

"The Americans deliberately put Moscow in a tough spot by having failed to inform it of the fact that (his) passport was annulled in time," the source said.

"The Russian authorities were informed of this post-factum, more than a week after Snowden was stripped of his passport," said the official.

"If this fact had been known in advance, then possibly Mr Snowden might not have flown to Moscow and this entire story might never have happened."

Russia and the United States do not have an extradition treaty and Moscow has thus far refused to hand over Snowden to Washington.

Russia's refusal - expressed personally by President Vladimir Putin earlier this week - has added to diplomatic tensions between Moscow and Washington that have existed due to the Syria crisis.

The Russian official said Snowden will only be able to leave Sheremetyevo airport after a country such as Ecuador or Venezuela offers him political asylum.

"On these grounds, he will legally leave the territory of Russia, without ever having crossed its border," the official said.