The head of UN Panel of Experts (PoE) Hugh Griffiths on Wednesday told members of U.S. Congress that he has not seen North Korean progress towards denuclearization, despite stricter sanctions regimes and two summits between Washington and Pyongyang.

Speaking at a House of Representatives Committee on Foreign Affairs hearing on how to make DPRK sanctions more effective, the UN investigator answered questions on a wide range of sanctions related topics.

But toward the start of the question and answer session, Griffiths said he had not seen either the current sanctions or diplomatic tracks yield results with regards North Korea’s nuclear