“We don’t want to talk about progress, we don’t want to talk about back channels,” Trump told reporters Friday, revealing nothing.

The diplomatic contacts are occurring regularly between Joseph Yun, the U.S. envoy for North Korea policy, and Pak Song Il, a senior North Korean diplomat at the country’s U.N. mission, according to U.S. officials and others briefed on the process. They weren’t authorized to discuss the confidential exchanges and spoke on condition of anonymity.

Officials call it the “New York channel.” Yun is the only U.S. diplomat in contact with any North Korean counterpart. The communications largely serve as a way to exchange messages, allowing Washington and Pyongyang to relay information.