Update 7:50 a.m. WikiLeaks founder Julian Assange says former National Security Agency contractor Edward Snowden has possibly applied for asylum in Ecuador, Iceland and possibly other countries.
Assange says he cannot go into detail about Snowden's whereabouts except to say that he is safe.
Snowden left Hong Kong Sunday to travel to Ecuador through Moscow and other points to avoid extradition to the U.S. He is facing espionage charges stemming from his disclosure of U.S. surveillance programs that collect phone records and online data in the name of foreign intelligence.
Snowden was not on a flight to Cuba Monday as expected. Ecuador says it is considering its asylum requests.
Ecuador granted Assange asylum last year. Assange is staying at the country's embassy in England to avoid extradition to Sweden to face questioning about sex crime allegations.
Assange's lawyer has said Snowden does not have many options for asylum.
Previously: U.S. Secretary of State John Kerry said Monday that it would be "deeply troubling" if Russia or Hong Kong had adequate notice about Edward Snowden's plans to flee to a country that will grant him asylum and still allowed him leave.
Snowden, a former National Security Agency contractor and a self-admitted leaker of state secrets, fled from Hong Kong to Moscow on Sunday after the U.S. moved to extradite him to face espionage charges. He was expected to seek political asylum in Ecuador.
He was booked on a flight from Moscow to Cuba on Monday, but he was not seen on the plane. Snowden's whereabouts are unknown. An Aeroflot representative who wouldn't give her name told The Associated Press that Snowden wasn't on flight SU150 to Havana. AP reporters on the flight couldn't see him.
It was unclear where he was or where he was he was trying to go, Kerry said. The U.S. has revoked Snowden's passport.
"We don't know, specifically, where he may head, or what his intended destination may be," Kerry said, responding to a question during a news conference in New Delhi where he was discussing bilateral issues between the U.S. and India.
He also was asked about whether the Snowden incident would affect the U.S. relationship with China and Russia.
"It would be deeply troubling, obviously, if they had adequate notice, and notwithstanding that, they make the decision willfully to ignore that and not live by the standards of the law," Kerry said.
"There is a surrender treaty with Hong Kong and if there was adequate notice - I don't know yet what the communication status was. But if there was, it would be very disappointing if he was willfully allowed to board an airplane ... and there would be, without any question, some effect and impact on the relationship and consequences. With respect to Russia, likewise."
The United States does not have an extradition treaty with Russia, but does with Cuba, Venezuela and Ecuador. Even with an extradition agreement though, any country could give Snowden a political exemption.
In the past two years, the U.S. has transferred seven prisoners to Russia that Moscow wanted, he said. "I think reciprocity and the enforcement of the law is pretty important," Kerry said, but he did not identify the law he was referencing.
Kerry also noted the countries involved in the incident.
"I suppose there is no small irony here. I mean, I wonder if Mr. Snowden chose China and Russian assistance in his flight from justice because they're such powerful bastions of Internet freedom, and I wonder if while he was in either of those countries he raised the question of Internet freedom since that seems to be what he champions."
Ecuador confirms Snowden seeking asylum there
Ecuador's foreign minister said Monday his country will act not on its interests but on its principles as it considers an asylum request from National Security Agency leaker Edward Snowden, wanted for revealing classified U.S. secrets.
Speaking to reporters in Hanoi, Foreign Minister Ricardo Patino said he could not comment on Snowden's location after the U.S. fugitive did not board a flight from Moscow to Cuba on which he was booked.
"I cannot give information with respect to that ... we cannot offer specific information about the specific situation of Mr. Snowden at this moment," he said.
Patino did not say how long it would take Ecuador to decide on Snowden's asylum request, which he said "has to do with freedom of expression and with the security of citizens around the world."
Snowden had been in hiding in Hong Kong for several weeks after revealing the spy programs. He flew to Moscow on Sunday and was booked on an Aeroflot flight to Cuba on Monday, but an airline representative said he didn't board the plane and AP reporters on the flight couldn't see him.
Patino said Ecuador was in touch with the highest authorities of Russia about the case.
"The government of Ecuador has maintained a respectful diplomatic contact with the government of Russia and has informed it that Ecuador is considering the petition for asylum on the part of Mr. Snowden," he said.
Patino read a letter from Snowden to Ecuador's president in which he asked for asylum "due to the risk of persecution by the government of the United States and its agents."
Snowden said in the letter that he revealed the information about the highly classified spy programs because the U.S. "is intercepting the majority of communications of the world."
"I have been accused of being a traitor" and "there have been calls for me to be executed or imprisoned," the letter said. He said it was unlikely that he could receive a fair trial.
Patino said Ecuador would not base its asylum decision on its potential to damage the country's relationship with the United States.
"There are some governments that act more upon their own interests, but we do not," Patino said. "We act upon our principles."
He added, "We take care of the human rights of the people."
Anti-secrecy group WikiLeaks earlier said Snowden was bound for Ecuador "via a safe route for the purposes of asylum, and is being escorted by diplomats and legal advisers from WikiLeaks." The organization's founder, Julian Assange, was granted asylum by Ecuador last year and has been staying at the country's embassy in the United Kingdom to avoid extradition to Sweden to face questioning about sex crime allegations.
This story has been updated.