The head of the U.N. panel monitoring sanctions against North Korea says the fact that the only thing Kim Jong Un asked for at the Hanoi summit was to have sanctions lifted shows they are biting — despite his increasingly sophisticated efforts to evade the tough measures.

Hugh Griffiths said in an interview Tuesday that the eight experts' message to Kim would be: "The Security Council is serious" and its resolutions "are very explicit."

The last sanctions resolution adopted unanimously by the council in December 2017 included sharply lower limits on North Korea's import of refined oil products and crude oil.

Griffiths noted that the resolution commits the Security Council to further restrict petroleum exports to North Korea if it conducts another nuclear test or launches an intercontinental ballistic missile.