Most recently, the New York channel was used to warn the State Department just before North Korea tested a nuclear bomb for the third time in February. North Korea is expected to test a medium-range ballistic missile as early as Wednesday and another warning could come to the Obama administration via North Korea's representative office at the U.N.
A former U.S. official who worked on North Korea in past administrations described how the New York channel works in an interview with The Cable just after the last nuclear test.
"It's been the main channel of communication between the North Korean government and the U.S. government. We don't have any other channels we use," the official said.
Han, the main official who runs the New York channel, also represented North Korea at two unofficial meetings with U.S. interlocutors in 2012 that were reported by The Cable, one in Singapore and one in Dalian, China. Hart attended the Dalian meeting.
The State Department declined to comment on the March New York meeting, in keeping with its past reticence to discuss the New York channel.
"They're afraid of their shadows," the former official said. "It's like 'No one can know we are actually communicating with these people because they are bad.'"
Secretary of State John Kerry is to visit China, South Korea and Japan later this week. A senior administration told CNN that Kerry will try to present a diplomatic path out of the crisis during his trip.