Edward Snowden says he repeatedly raised constitutional concerns about National Security Agency surveillance internally, but an NSA search turned up a single e-mail in which Snowden gently asks for "clarification" on a technical legal question about training materials, agency officials said.

Snowden, a former NSA systems administrator whose leaks have exposed some of the agency's most sensitive spying operations, called himself a patriot in an interview this week with NBC News' Brian Williams.

Asked by Williams whether he first raised his qualms with his bosses, he said, "I reported that there were real problems with the way the NSA was interpreting its legal authorities."