Snowden: Long prison term for me would erode democracy in US

Edward Snowden is seen on a television screen via video uplink from Moscow during a news conference to call upon President Barack Obama to pardon Snowden before he leaves office, Wednesday, Sept. 14, 2016, in New York. Human and civil rights organizations, including the ACLU, Human Rights Watch and Amnesty International, launched a public campaign to persuade Obama to pardon the former National Security Agency contractor, who leaked classified details in 2013 of the U.S. government's warrantless surveillance program before fleeing to Russia. (AP Photo/Mary Altaffer) (The Associated Press)

Dinah PoKempner, left, general council for Human Rights Watch, listens as Edward Snowden speaks on a television screen via video link from Moscow during a news conference to call upon President Barack Obama to pardon Snowden before he leaves office, Wednesday, Sept. 14, 2016, in New York. Human and civil rights organizations, including the ACLU, Human Rights Watch and Amnesty International, launched a public campaign to persuade Obama to pardon the former National Security Agency contractor, who leaked classified details in 2013 of the U.S. government's warrantless surveillance program before fleeing to Russia. (AP Photo/Mary Altaffer) (The Associated Press)

Naureen Shah, director of Amnesty International USA's Security & Human Rights Program, holds up a photo of Edward Snowden during a news conference to call upon President Barack Obama to pardon Snowden before he leaves office, Wednesday, Sept. 14, 2016, in New York. Human and civil rights organizations, including the ACLU, Human Rights Watch and Amnesty International, launched a public campaign to persuade Obama to pardon the former National Security Agency contractor, who leaked classified details in 2013 of the U.S. government's warrantless surveillance program before fleeing to Russia. (AP Photo/Mary Altaffer) (The Associated Press)

National Security Agency leaker Edward Snowden says it would "chill speech" and "erode the quality of our democracy" if he serves a long prison term in the U.S.

Snowden spoke by video at a New York news conference Wednesday. Advocates, including Human Rights Watch and Amnesty International, are launching a public campaign to persuade President Barack Obama to pardon him.

Speaking from Moscow where he is in exile, Snowden said he performed a public service by giving thousands of classified documents to journalists in 2013.

He says whistleblowers are "democracy's safeguard of last resort."

White House spokesman Josh Earnest said Monday that the president believes Snowden should return to the U.S. to face charges. He said Obama's position is that Snowden's leaks harmed national security and put Americans at risk.