If President Trump meets Kim Jong-un, the son of the dictator who made the offer to Mr. Clinton, the challenge of verifying that North Korea is on the way to disarmament will be far, far greater than it was nearly two decades ago. In the years since, the North has tested six nuclear weapons and, according to American intelligence agencies, has 20 to 60 more.

Its missile program is now vast, including intercontinental missiles that may be able to hit the United States and mobile missiles that can be hidden in tunnels around North Korea before being pulled out and launched quickly.

“Diplomacy is a good step but verification is key,” said Wendy Sherman, who was in the Oval Office during that visit on Oct. 11, 2000, and traveled with Ms. Albright on that ultimately unsatisfying trip.

There would need to be “site inspections everywhere necessary, as we negotiated for Iran,” Ms. Sherman said, a small dig at Mr. Trump, who has complained that the 2015 nuclear deal with Tehran left too much room for cheating. “Kim is in the driver seat — he has many nuclear weapons and he knows where all of them are. We don’t.”

As with much diplomacy in the Trump era, this one is happening without a full playbook.

The usual approach would be to negotiate the details first — defining the scope of any agreement, including fundamental questions like whether it would be limited to the nuclear and missile programs or would include the North’s conventional and cyber weapons.