US President Donald Trump has said he will "consider" the case of Edward Snowden, a former National Security Agency (NSA) operative and whistleblower living in exile in Russia, and will consider his possible pardon.

"I am not fully aware of Snowden's situation. "Many people think he should be treated differently, and some others believe he did a lot of bad things," Trump told reporters.

He added that he would consider the case very "intensively".

U.S. officials have wanted Snowden to return to the United States for years to face criminal charges in connection with 2013 espionage charges.

Snowden fled the United States and was granted asylum in Russia after he leaked secret documents to the media revealing that the NSA was conducting spy operations at home and abroad.