RUTHFULLY YOURS

Realism is warranted. The hopeful case is that the North’s reversal is a response to the Trump Administration’s policy of pressure through tighter sanctions and diplomatic isolation. Building on United Nations sanctions, the Treasury Department has been blacklisting companies, most of them Chinese, for trading with the North.

As the Journal reported last week, trade across the border with China has declined sharply. Despite its official ideology of self-sufficiency, the North depends on imports of energy, food and raw materials to survive. It also needs luxury goods to reward top officials.

The Trump Administration’s threats of military action if sanctions don’t work may also have secured more Chinese cooperation, even if a military strike carries huge risks. Beijing has been forced to consider the possibility of conflict between nuclear states on its doorstep. It’s also notable that the North told South Korean officials that it agreed to the U.S. demand to halt nuclear and missile tests while talks are underway. Perhaps Mr. Trump’s tough line wasn’t as dangerous and destabilizing as his critics claimed.

Yet the U.S. and the world should still be skeptical that Kim will really put his nukes on the negotiating table. Kim’s father and grandfather used talks to stall for time while they continued the nuclear program in secret. They also extracted concessions in return for talking and broke every promise they made.

The new diplomacy offer also follows a familiar Pyongyang pattern. First make nuclear or missile advances that increase its threat to South Korea and the world. Then make a diplomatic bid once a dovish government takes over in Seoul. This time Kim took advantage of the recent Olympic games and the aching, almost palpable, desire of new South Korean President Moon Jae-in for talks.

The South Koreans said North also demanded “security guarantees,” which it may define as the departure of U.S. forces from Korean peninsula. That would be a security and geopolitical disaster as long as the North retains its military threat.

China will want the U.S. to end its military exercises with the South in return for the North “freezing” its nuclear program. The U.S. and South postponed training at the North’s request to encourage its participation in the Olympics. But another delay would be the wrong precedent for talks, especially as the exercises are critical to deterring the North’s conventional military threat.

The temptation for the Trump Administration will be to accept partial denuclearization in return for some normalization of relations. But that wouldn’t end the nuclear threat, and it would give the North the whip hand to extract concession after concession lest it revive an active nuclear program. This is what the North did after George W. Bush lifted sanctions and took North Korea off the list of terrorist-sponsoring states. When it didn’t immediately get everything it wanted, the North reneged.

To have any chance of success, the U.S. and U.N. will have to keep sanctions in place during the talks. The U.S. and South Korea will also have to stay united on strategy, since Kim’s foremost goal will be to divide the two and coax the South to push U.S. forces out.

Any deal must be structured so that the North is rewarded only after it denuclearizes and allows unlimited inspections. If financial and military pressure really is what coaxed Kim to this pass, then the pressure must be maintained. Barack Obama’s Iran deal is the example not to follow.