The hunt for Edward Snowden

(CBS News) WASHINGTON - Edward Snowden is the most wanted fugitive in the world Monday night.

The White House believes the former NSA contract employee, charged with espionage, is in Russia, and the United States has been pressuring the Russians all day to send him home before he can head into asylum in some other country.

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The incident has strained U.S. relations with both Russia and China.

It was in Hong Kong that Snowden exposed two top-secret U.S. surveillance programs -- one collects the phone records of millions of Americans, the other monitors internet traffic.

For now, Snowden's flight to an unknown refuge appears stalled in Moscow. As of Monday night, seat 17A -- which Snowden had reportedly booked on this Cuba-bound jetliner -- remained empty as the plane took off for Havana, Cuba.

It's not clear if Snowden changed travel plans or if Russian security agents blocked his departure. But, U.S. officials are pressing the Russian government to detain Snowden as a fugitive travelling with a revoked passport. Jay Carney is the White House press secretary.

"We have asked the Russians to look at the options available to them to expel Mr. Snowden back to the United States," White House press secretary Jay Carney told reporters Monday afternoon.

Carney urged Russia not to repeat the actions of Chinese authorities, who allowed Snowden to leave Hong Kong on Sunday.

"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," he said.

Snowden originally pledged to fight extradition from Hong Kong, but, after the U.S. Justice Department revealed Friday, it had charged him under the Espionage Act. Snowden ran.

Watch: John Miller describes the events leading up to Edward Snowden's escape from Hong Kong.

How Snowden got away, CBS News correspondent John Miller explains, is unclear. "We didn't hear a lot about it while it was going on, but it was fairly fast-paced and in some ways, I think, fooled the U.S. authorities into thinking it would be working mechanically the way it was supposed to." he told "CBS Evening News" anchor Scott Pelley.

The anti-secrecy whistleblower group Wikileaks orchestrated and paid for Snowden's escape. Accompanied by a WikiLeaks advisor, Snowden flew to Moscow. From there, he was expected to fly to Cuba, and then to Ecuador, where authorities are now considering his bid for political asylum.

In a phone conference with reporters, Wikileaks founder Julian Assange refused to divulge Snowden's current location.

"We are aware of where Mr. Snowden is, he is in a safe place," Assange said. And his spirits are high."

Assange spoke from Ecuador's embassy in London where he has taken refuge for more than a year. If Snowden can get to Ecuador, he may be safe. While the U.S. has an extradition treaty with Ecuador, authorities there would not be inclined to cooperate in what they view as a politically motivated prosecution.

It's possible that Russian President Vladimir Putin may want to extract a price for turning over Snowden. That could involve some kind of trade or diplomatic favor. But, he's taking his time, putting the U.S. in the embarrassing position of desperately pleading for help

In an interview with CBS News correspondent Margaret Brennan in New Delhi, Secretary of State John Kerry said the U.S. is doing everything it can to bring Snowden back home.

It's "an effort to try to persuade our Russian colleagues that this is important to the U.S. (and) important to them," he said, adding that the U.S. has "returned seven prisoners to (Russia) in the last two years that they requested. I think it's very important to them to adhere to the rule of law and respect the relationship."