While the approach could stop that arsenal from growing, it would not, at least in the near future, dismantle any existing weapons, variously estimated at 20 to 60. Nor would it limit the North’s missile capability.

The new approach tacitly accepts the North as a nuclear power — something administration officials have often said they would never stand for. Still, it is a significant — but limited — first step.

Details: American negotiators would seek to expand on Mr. Kim’s previous offer to give up the country’s main nuclear-fuel production site, at Yongbyon, in return for a lifting of the most onerous sanctions against the country. (Mr. Trump rejected that proposal.)

The goal now is to get Mr. Kim’s new negotiating team to agree to expand the definition of the Yongbyon site well beyond its physical boundaries.

Complications: A senior U.S. official involved in North Korean policy said there was no way to know whether North Korea would agree to such a deal. In the past, he said, its negotiators have insisted that only Mr. Kim could decide those boundaries. And the North would have to accept intrusive inspections.