WASHINGTON – Defiant and apparently unbowed by threats of prosecution, former National Security Agency contractor Edward Snowden vowed Monday to release more secrets about U.S. intelligence surveillance systems that he described as “nakedly, aggressively criminal.”

Snowden, who has been hiding in Hong Kong, said NSA analysts routinely obtain emails and other Internet communications of Americans as part of the cyberspying agency’s surveillance of global telecommunications and Internet traffic.

Writing in a chat on the website of Britain’s Guardian newspaper, Snowden said U.S. communications are “collected and viewed on a daily basis” by NSA analysts operating without a specific warrant. “They excuse this as ‘incidental’ collection, but at the end of the day, someone at NSA still has the content of your communications.”

Internal audits that show the NSA is not spying on Americans “are cursory, incomplete and easily fooled by fake justifications,” Snowden said.

U.S. intelligence officials did not respond to Snowden’s statements. Former NSA officials rejected his portrayal, however, saying the agency follows strict procedures to keep confidential any names of Americans caught up in monitoring efforts aimed at foreign terrorists, and sharply limit who can see the data.

“His premise is just false,” said a former NSA official who asked not to be identified in discussing classified programs. “What he’s saying is like a quarter true, but it’s the worst kind of truth, because it’s fundamentally misleading.”

The former official said the name of an American inadvertently monitored would be blacked out in any intelligence report, and that the communications could be examined only for foreign intelligence relevance. Further investigation would require involvement of the FBI and probably a warrant, the former officials said.

“It’s true, you could come in and search for anything that you wanted, but you have to provide a justification, and those justifications are reviewed,” the former NSA operator said. “If you wanted to search a U.S. phone number, that would be an enormous red flag.”

President Barack Obama, in an interview taped Sunday with PBS talk show host Charlie Rose, said he has asked intelligence agencies to determine whether more details about the classified programs can be released without compromising their usefulness.

“They are in that process of doing so now, so that everything that I’m describing to you today, people, the public, newspapers can look at,” Obama said. “Because frankly, if people are making judgments just based on (what has) been leaked, they’re not getting the complete story.”