Snowden, a former National Security Agency (NSA) contractor, is in Russia after arriving Sunday from Hong Kong, hoping to win asylum in Ecuador and evade arrest after leaking sensational details of secret US surveillance programmes of Internet and phone data.
He has infuriated and embarrassed Washington with a series of leaks that have strained diplomatic ties between the US and countries that have failed to extradite him despite a warrant by American authorities.
"It (the request) has to do with freedom of expression and the security of citizens around the world," he added.
"We always act by principle not in our own interest. There are some governments who act more on their own interests, we do not."
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The 30-year-old IT contractor was expected to head to Ecuador via Cuba and AFP correspondents at Moscow's Sheremetyevo airport saw an Ecuadoran flagged diplomatic car at VIP arrivals.
"We know he is in Moscow, we're in talks with higher authorities," Patino, who is on an official visit to communist Vietnam, said.
US authorities have been left red-faced by Snowden's revelations of intelligence trawling by the NSA of phone call logs and Internet data, prompting concern from governments around the world and outrage from privacy campaigners.
Snowden made the revelations from Hong Kong which allowed him to travel to Moscow, a decision described as "troubling" by US authorities who have laid charges including of theft and espionage against the whistleblower, revoked his passport and sought his extradition.
"If he has asked for asylum in Ecuador then they could give him a refugee document or even Ecuadoran citizenship allowing him to continue his journey," a security source told Interfax.
Snowden's dramatic evasion of US authorities has stirred tensions between Washington and Moscow and Beijing -- which retains ultimate control over Hong Kong.