WASHINGTON — Stephen J. Kim, a former State Department contractor charged with leaking information from a highly classified report about North Korea to a Fox News reporter in 2009, pleaded guilty on Friday and agreed to serve a 13-month prison sentence.

Mr. Kim became the sixth official to be convicted in a leak-related prosecution by the Obama administration, which has pursued eight such cases to date. Only three leak cases were prosecuted under all previous administrations.

Mr. Kim’s leak led Fox News to report in June 2009 that “the Central Intelligence Agency has learned, through sources inside North Korea” that North Korea was likely to respond to a United Nations resolution condemning its nuclear and missile tests with even more tests. C.I.A. officials were said to be furious that a top-secret analysis had been leaked almost as soon as it had been written.

While critics of the crackdown on leaks have accused the Obama administration of waging a war on whistle-blowers, Mr. Kim agreed to say that he did not believe that he was bringing waste, fraud, abuse or other misconduct to light.