The head of the National Security Agency said on Sunday he did not know why his agency failed to prevent former NSA contractor Edward Snowden from leaving Hawaii for Hong Kong with a trove of secrets about U.S. surveillance programs.
"It's clearly an individual who's betrayed the trust and confidence we had in him. This is an individual who is not acting, in my opinion, with noble intent," General Keith Alexander told the ABC News "This Week."
Snowden had been working as a contractor for the NSA in Hawaii when he fled to Hong Kong and he flew to Moscow on Sunday. He is now charged with espionage and is seeking asking asylum from Ecuador.
Related: US warns against Snowden Travel; Fugitive Seeks Asylum
Asked if he knew why the NSA did not catch Snowden before he left Hawaii, Alexander said: "No, I don't."
Alexander told ABC News’ George Stephanopoulos that Snowden has caused “irreversible and significant damage” to the U.S. with his actions.
He also said his agency is taking steps to ensure this doesn't happen again.
"We are now putting in place actions that would give us the ability to track our system administrators, what they're doing, what they're taking, a two-man rule," he told ABC. "We've changed the passwords. But at the end of the day, we have to trust that our people are going to do the right thing. This is an extremely important mission defending our country.
"When they betray that trust, well, then we have to push it over to the Department of Justice and others for the appropriate action."
The United States is hoping for cooperation from foreign countries to bring Snowden home to face charges.
The State Department on Sunday warned countries in the Western Hemisphere that Snowden might travel through or take refuge in not to let the former spy agency contractor go anywhere but home, a State Department official said.
"The U.S. is advising these governments that Snowden is wanted on felony charges, and as such should not be allowed to proceed in any further international travel, other than is necessary to return him to the United States," the official said in a written statement on Sunday.
Alexaner defended the actions of his department as a necessary step to keep Americans safe.
"The fact is what we're trying to do is get the information our nation needs, the foreign intelligence, that primary mission, in this case and the case that Snowden has brought up is in defending this nation from a terrorist attack," he said.
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