"I'm not counting on it," Snowden said in an interview published by Yahoo News on Monday.
The former National Security Agency contractor leaked thousands of classified documents to the press in 2013 which revealed the vast scope of US surveillance of private data that was put in place after the 9/11 attacks.
After fleeing his home in Hawaii, he now lives in exile in Russia where he has sought asylum.
Should he ever return to the United States, Snowden would be tried for espionage and other charges carrying up to 30 years in prison.
Since September, there has been a campaign calling for a presidential pardon that has won support from figures such as financier George Soros and Twitter CEO Jack Dorsey.
The campaign says Snowden should be welcomed home "as a hero" for actions that benefited the public because they reined in US surveillance programs and led to improved privacy protection laws.
Snowden's lawyers are trying to win him clemency before Obama leaves office in January or a plea bargain that would shield him from spending a lot of time in jail.
Copyright AFP (Agence France-Presse), 2016