And he says intelligence officials in China as well as Russia could not get access to the documents he had obtained before leaving the US.
In an interview with The New York Times, Mr Snowden said he handed over all the documents he had obtained to journalists during his stay in Hong Kong.
Mr Snowden said he did not retain copies of the documents and did not take them to Russia "because it wouldn't serve the public interest," the newspaper reported.
He said his familiarity with China's intelligence abilities allowed him to protect the documents from Chinese spies while he was in Hong Kong.
"There's a zero per cent chance the Russians or Chinese have received any documents," he said.
Mr Snowden's leaks of highly classified material have resulted in numerous news stories about US surveillance activities at home and abroad, and sparked debate about their legality, and the privacy implications for average Americans.
The newspaper reported the interview took place over several days in the past week and involved encrypted online communications.
It said Mr Snowden asserted he believed he was a whistleblower who was acting in the nation's best interests.