A television screens the image of former US spy agency contractor Edward Snowden during a news bulletin at a cafe in Moscow's Sheremetyevo airport on June 26, 2013. Russian President Vladimir Putin confirmed on Tuesday that Snowden, sought by the United States, was in the transit area of a Moscow airport but ruled out handing him to Washington. [Photo/Agencies]

MOSCOW -- A former US spy agency contractor facing charges of espionage remained in hiding at a Moscow airport on Wednesday while the prospect grew of a protracted Russian-US wrangle over his fate.

Ecuador, where Edward Snowden has requested asylum, said a decision could take months and asked Washington to argue its case for extradition. Russia said Snowden, whose flight is proving a growing embarrassment for President Barack Obama, was still in the transit area of Sheremetyevo airport.

Snowden fled the United States to Hong Kong this month after leaking details of secret US government surveillance programmes, then flew on to Moscow on Sunday.

He has not been seen in the transit area - the zone between the departure gate and formal entry into the country - since his arrival, although a receptionist at a hotel in the transit zone said he looked at the prices there on Sunday, then left.

Russian President Vladimir Putin has denied that Snowden was being interviewed by Russian intelligence and called any U.S. accusations that Moscow was aiding him "ravings and rubbish".

There was no sign of Snowden registering for onward flights out of Russia on Wednesday.

"They are not flying today and not over the next three days," an Aeroflot representative at the transfer desk at Sheremetyevo said when asked whether Snowden and his legal adviser, Sarah Harrison, were due to fly out. "They are not in the system."

U.S. Defense Secretary Chuck Hagel said on Wednesday that Snowden's leaks to news media had been a serious breach that violated US laws and damaged its national security. He repeated calls for Moscow to hand him over.

"I would hope that the Russians do the right thing here," Hagel told a Pentagon news conference, adding that Moscow evidently had not made a final decision since Snowden reportedly was still at the airport.

'Serious security breach'

"He has broken laws," Hagel said. "There was damage done to this country by the Snowden leaks. We are assessing that now but make no mistake, this violation of our laws was a serious security breach."

Putin has said he will not extradite Snowden. By declaring that he is in the transit area, Russian authorities maintain the position that he has not formally entered Russia - a step that would take the dispute to another level.

Russian law requires travellers who spend more than 24 hours in the airport's transit area - as Snowden has done - to obtain a transit visa, which in some cases is valid for three days.

It is unclear whether Snowden has sought or received one, and if so when it would expire. The United States said on Sunday it had revoked Snowden's passport.

Several people, mainly refugees, have been able to stay in Moscow's airports for months.

What is clear is that the longer the situation remains unresolved, the more it could fray US-Russian ties.

The former Cold War-foes are already at odds over human rights and Putin's treatment of opponents and have squared off over the Syria conflict in the UN Security Council.

The United States has no extradition treaty with Moscow, but says there is a clear legal basis for Snowden to be handed over. White House spokesman Jay Carney said on Wednesday that US and Russian officials were "having conversations" on the issue, but declined to give details.

Carney told reporters while travelling with Obama to Africa that Washington could understand that Snowden's decision to go to Moscow "creates issues the Russian government has to consider."

"We also believe that when it comes to Mr. Snowden, well, we agree with President Putin that we don't want the situation to harm our relations, he said.  

Russian Foreign Minister Sergei Lavrov on Wednesday repeated Putin's stated opinion that Snowden should choose a destination and fly out as soon as possible, state-run Itar-Tass news agency reported.

Putin, a former KGB officer, may feel little sympathy for someone who has broken the secrecy code. He has suggested the surveillance methods revealed by Snowden were justified in fighting terror, if carried out lawfully.