As Secretary of State Mike Pompeo concludes his latest visit to Pyongyang, North Korea, it is time for President Trump to drop his rosy talk about Kim Jong Un, which has become less and less convincing, and demand that the tyrant demonstrate that he wants a serious deal that furthers the cause of international peace.

Trump brought America’s ardent enemy to the negotiating table, for which he will deserve credit if it produces results. But North Korea continues its research on technology for ballistic missile engines and targeting, on re-entry vehicles to deliver nuclear warheads, and on the weaponization of nuclear materials. These activities not only threaten America, but also embolden Kim and teach him that he can gain concessions at little or no cost.