NEGOTIATIONS BETWEEN the United States and North Korea have been stalled for months, so the announcement on Friday that President Trump will hold a summit next month with Kim Jong Un is a step forward. That confirmation came after Pyongyang’s chief negotiator, Kim Yong Chol, met with Mr. Trump and Secretary of State Mike Pompeo; other talks between lower-ranking officials are reportedly in progress. Negotiations are better than the preceding stalemate, during which North Korea is believed to have continued developing its nuclear weapons and missile programs, while taking no concrete steps toward disarmament.

Still, the resumption of diplomacy reflects another tactical victory by the Kim Jong Un regime over a divided and inept U.S. administration. Following the Trump-Kim summit in Singapore, U.S. officials pressed North Korea’s regime to show its seriousness about giving up nuclear weapons by providing an inventory of its warheads and production facilities. The regime angrily refused and stiffed Mr. Pompeo, even as it showered Mr. Trump with flowery letters said to be from Mr. Kim. Now it has apparently gotten its way: It is negotiating directly with Mr. Trump, who has professed himself to be entranced by the letters and “in love” with Mr. Kim.

At the last summit, in Singapore, Mr. Trump spontaneously offered a significant concession — the suspension of U.S. military exercises with South Korea — in response to what he said was a request from Mr. Kim, taking South Korea and even U.S. military commanders by surprise. The North Koreans no doubt hope they can manipulate Mr. Trump into new giveaways at a second summit, such as a relaxation of sanctions, a declaration ending the Korean War, or even the withdrawal of U.S. troops from South Korea. They have given no indication they will offer anything substantive in return. At a meeting with the South Korean president last fall, Mr. Kim floated the shutdown of the aging nuclear facility at Yongbyon — a horse that has been peddled in previous negotiations.

Mr. Trump’s diplomacy has not been fruitless: North Korea has now refrained from nuclear or missile tests for 13 months, breaking what looked, in Mr. Trump’s first year in office, like a slide toward war. In his New Year’s address, Mr. Kim asserted that the regime will not “produce, test nor proliferate any more nuclear weapons.” But the regime has never made an unambiguous commitment to give up its arsenal of warheads and missiles, and Mr. Kim’s speech reverted to Pyongyang’s hard-line positions. He said that no steps would be taken until sanctions on the country were lifted, and that denuclearization must include the withdrawal of U.S. forces and assets from the region.

Perhaps there have been hints of greater flexibility in those letters Mr. Trump has been waving around. But the danger is that Mr. Kim will use a second summit to persuade a gullible U.S. president to yield valuable concessions in return for fool’s gold. We’d like to hope that Mr. Trump’s advisers, such as Mr. Pompeo, would dissuade him from reckless action; but then, as the president’s recent decision to order U.S. troops out of Syria showed, he’s not inclined to listen. All of which means that a resumption of U.S.-North Korean negotiations should be welcomed — but warily.

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