Edward J. Snowden, the former National Security Agency contractor, said in an extensive interview this month that he did not take any secret N.S.A. documents with him to Russia when he fled there in June, assuring that Russian intelligence officials could not get access to them.

Mr. Snowden said he gave all of the classified documents he had obtained to journalists he met in Hong Kong, before flying to Moscow, and did not keep any copies for himself. He did not take the files to Russia “because it wouldn’t serve the public interest,” he said.

“What would be the unique value of personally carrying another copy of the materials onward?” he added.

He also asserted that he was able to protect the documents from China’s spies because he was familiar with that nation’s intelligence abilities, saying that as an N.S.A. contractor he had targeted Chinese operations and had taught a course on Chinese cybercounterintelligence.