The U.S. chief nuclear negotiator on Friday said Washington is yet to receive any indication that Pyongyang is interested in talks, expressing reservations about a two-month pause in missile and nuclear tests by the North.

“I hope that they will stop forever,” Joseph Yun, Special Representative for North Korea Policy, said at a news conference in Jeju, South Korea, in comments carried by Seoul’s Yonhap News Agency.

“But we had no communication from them so I don’t know whether to interpret it positively or not. We have no signal from them.”

Yun told a closed-door panel at the Council on Foreign Relations