Edward Snowden has highly sensitive documents on how the National Security Agency is structured and operates that could harm the U.S. government, but has insisted that they not be made public, a journalist close to the NSA leaker said.

Glenn Greenwald, a columnist with The Guardian newspaper who first reported on the intelligence leaks, told The Associated Press that disclosure of the information in the documents "would allow somebody who read them to know exactly how the NSA does what it does, which would in turn allow them to evade that surveillance or replicate it."

He said the "literally thousands of documents" taken by Snowden constitute "basically the instruction manual for how the NSA is built."....