Details have begun emerging about what kept US President Donald Trump and North Korean leader Kim Jong-un apart in their denuclearization talks in Hanoi last week. As expected, Kim is to blame for the breakdown.

US national security adviser John Bolton led off the revelations about the discussions Trump and Kim had in the Vietnamese capital, where they ended their talks without an agreement.

In three recent successive TV interviews, Bolton said Trump gave Kim a “big-deal” document listing what the North should do in return for economic rewards. The talks broke down because Kim did not accept Trump’s proposal, and this should raise doubts as to Kim’s commitment to disarmament.

A good part of what happened in Hanoi was that Trump pointed to the North’s weapons of mass destruction like chemical and biological arms, as well as its nukes and ballistic missiles. That countered presummit speculation that Trump would lower the bar to make an agreement for the sake of an agreement.

“The issue, really, was whether North Korea was prepared to accept what the president called ‘the big deal,’ which is denuclearize entirely under a definition the president handed to Kim Jong-un, and have the potential for an enormous economic future,” Bolton said in one of the interviews.

Bolton’s comments show that Kim sought relief of sanctions imposed on his regime over its nuclear and missile provocations by offering what the US side described as “limited concessions.”

They include the dismantling of an outdated nuclear reactor in Yongbyon, and parts of uranium-related facilities and plutonium-reprocessing facilities in other areas.

In short, Kim tried to get sanctions relief in exchange for partial disarmament. Trump did well to walk away from the talks.

After the summit, the North Korean side disclosed its intention. It rebutted Trump’s comments that Kim wanted the lifting of “all sanctions,” insisting Pyongyang was seeking only partial relief of sanctions from the US.

In reality, however, the five sanctions the North listed have all been imposed since 2016 and thus constitute key elements of the harshest-ever international sanctions slapped on the North.

Another positive element in the US position is that -- Bolton made it clear in the interviews -- Washington could toughen the sanctions if the denuclearization process does not proceed well. The security adviser especially mentioned reinforcement of crackdowns on ship-to-ship transfers to North Korea of banned items like oil.

This, of course, should not mean that the US will only stick to a hard-line position. It was sensible in this regard that both Trump and Bolton left open future negotiations between working-level officials of the two sides.

In this context, a mediation by South Korean President Moon Jae-in would be able to facilitate the follow-up discussions between the US and the North. Moon’s top hand on North Korea, Lee Do-hoon, left for Washington on Tuesday to meet the US negotiator with the North, Stephen Biegun, and there is also talk of Moon sending a special envoy to Pyongyang.

An early visit to Seoul by Kim, which the North Korean leader promised when Moon visited Pyongyang in September last year, also would be able to help accelerate the denuclearization process.

All such peace and reconciliation steps toward North Korea, however, should be separated from appeasement, which could only embolden the Kim regime.

The US and South Korean militaries’ decision to cease the two massive springtime joint military exercises is one good case of appeasement in point.

A big cause for concern is that Trump continues to link the South Korea-US joint drills to his “America First” policy. He said after the Hanoi summit that he wanted to save “hundreds of millions of dollars” for the US for which the US is not reimbursed. He added in his tweet that “Also, reducing tensions with North Korea at this time is a good thing!”

But he need look no further than the months since his first meeting with Kim in June, after which he unilaterally announced suspension of another major joint drill held annually in the fall. It might have saved the US some money, but it has had little effect on encouraging the North to speed up denuclearization.

It should be a reminder for both Trump and Moon that they need to work together to maintain sanctions and a strong military alliance until substantial progress in disarmament is made.