A former U.S. State Department arms expert, Stephen Kim, on Friday pleaded guilty to leaking secret information on North Korea to the media.

Kim, a Korean-American, is charged with revealing classified information about the possibility of a North Korean nuclear test to a Fox News reporter in 2009.

At a U.S. federal court hearing here, Kim pleaded to "one count of making an unauthorized disclosure of national defense information," the Justice Department said.

The information concerned the military capabilities and preparedness of North Korea, it added.

"Today, Stephen Kim admitted to violating his oath to protect our country by disclosing highly classified intelligence about North Korea's military capabilities," said U.S. Attorney Ronald Machen. "Stephen Kim admits that he wasn't a whistleblower. He admits that his actions could put America at risk."

Under a plea bargain, the 46-year-old faces a 13-month prison term to be followed by a year of supervised release, it added. His Korean name is Kim Jin-woo.

If it is accepted by a federal judge, the sentence will be handed down on April 2.

It would end almost four years of a closely watched legal process.

The Kim case has been viewed as a test of the Barack Obama administration's handling of espionage issues. Some argued that severe punishment against Kim would damage press freedom.

They claim the leaked information was not directly associated with national security or the well-being of Americans. (Yonhap)