THE STALL in U.S.-North Korea negotiations was seeded in President Trump’s hasty and slipshod diplomacy with dictator Kim Jong Un this year. Mr. Trump impulsively agreed to a summit with Mr. Kim on the basis of vague assurances from South Korea, then rushed to carry it out without adequate preparation. At the Singapore meeting in June, Mr. Trump did not insist on a clear North Korean commitment to give up its nuclear weapons even as he pledged to “establish new . . . relations” with Pyongyang and “build a lasting and stable peace regime on the Korean Peninsula.” The predictable result is that North Korea is proceeding with its production of fissile material and missiles while demanding that Mr. Trump deliver on his promises.

In an attempt to regain some leverage, Mr. Trump last Friday announced the cancellation of a planned visit to Pyongyang by Secretary of State Mike Pompeo. But the president is in a bind of his own making. Encouraged by his grandiose declaration after Singapore that North Korea was “no longer a Nuclear Threat,” South Korea’s dovish government has pressed ahead with its own plans to expand economic ties with Pyongyang. President Moon Jae-in is backing Mr. Kim’s demand that the United States join in a declaration ending the Korean War. Pointing to the text of the deal Mr. Trump negotiated, North Korean negotiators insist that must come before any steps toward denuclearization.

Mr. Trump sought to blame China for the impasse, tweeting , “I do not believe they are helping with the process of denuclearization as they once were” because of “our much tougher Trading stance.” But Mr. Trump himself condoned a loosening of Chinese sanctions enforcement back in June, saying “President Xi [Jinping] of China . . . has really closed up that border, maybe a little less so over the last couple of months, but that’s okay.” And if it is true that China has relaxed pressure on Pyongyang, Mr. Trump must bear responsibility. Senior Chinese officials say Mr. Trump reneged on a pledge not to initiate a trade war in exchange for Beijing’s help on North Korea.

In Twitter posts last Friday, Mr. Trump further entangled the two issues, suggesting that negotiations with North Korea would “most likely” not resume until “after our Trading relationship with China is resolved.” But negotiations with China also appear stuck. Is it Mr. Trump’s intention to allow North Korea to keep building its capacity to strike the United States with nuclear weapons until China makes concessions on steel exports or technology transfers? That is a senseless and dangerous mix-up of unrelated objectives.

The administration’s best hope of rescuing the situation is to return to talking with North Korea about an equitable tradeoff. To start the process of denuclearization, U.S. officials say the Kim regime must provide a complete inventory of its assets — warheads, production facilities and other nuclear infrastructure — and agree to inspections to verify it. Previous negotiations have broken down because of Pyongyang’s refusal to take this step, so a full disclosure would provide the first clear signal that Mr. Kim was serious about denuclearization. That, along with a freeze in the production of missiles and fissile materials, could justify U.S. participation in the end-of-conflict declaration the two Koreas are seeking.

What doesn’t make sense is for Mr. Trump to suppose that he can disarm North Korea through trade talks with China — or by canceling meetings on Twitter.

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