As presidential letters go, this one was nothing short of extraordinary. As letters between human beings in general go, it was quite … what? Wistful? Heavyhearted? Melancholy, even?

The sudden note on White House stationery emerged Thursday morning from U.S. President Donald Trump to North Korean leader Kim Jong Un, canceling plans for a high-stakes Singapore summit. It was unexpected in both its existence and its appearance just hours after the American president got part of what he wanted — the demolition of a nuclear test site in the North.

To someone reading it cold and looking for deeper meaning, the three-paragraph letter was a stylistic theme park of the openly spoken and the implied — at turns tough-talking screed, respectful exchange and subtle hint at a possible way forward.

Embedded in it, too, was a recurring tone that felt almost intimate in its wording — not to mention its sometimes un-Trumpian voice.

Twitter’s chattering class immediately and predictably had a field day calling it a breakup letter (“the clingiest,” one tweet said), which probably went a step too far. The letter was, however, suffused with twinges of regret that walked right up to the line of implying that, in effect, “I just think we should take a break for a while and then see how we feel.”

Did Trump draft the letter himself, or did he enlist a West Wing Cyrano for help? According to Republican Sen. Cory Gardner, the president dictated it to National Security Adviser John Bolton and then signed off with his kinetic, EKG-style signature.

It did feature the occasional familiar Trumpian flourish (“totally irrelevant”; “truly sad”) that Twitter has conditioned us to expect. But those who spend their days trying to decipher the complex, often contradictory being that is the current American president could find a great deal of fresh food for thought to chew on.

Such as:

—SAYING HI. Trump addressed the letter to “His Excellency.” Standard protocol, undoubtedly, but also strikingly different and roundly respectful from a chief executive who mere months ago was calling Kim “Little Rocket Man.”

—I’M GRATEFUL. Not something the American president typically offers up to North Korea. “I want to thank you for the release of the hostages who are now home with their families. That was a beautiful gesture and very much appreciated.” (Still unclear: how Kim might view the description of them as “hostages”; North Korea might call them criminals.)

—THE PERSONAL TOUCH. “I was very much looking forward to being there with you,” Trump wrote, making the political personal when he might have easily said something like, “The United States was eagerly anticipating the opportunity to meet and discuss mutual pressing issues.”

Trump also told Kim that he “felt a wonderful dialogue was building up between you and me,” another friendly nod that takes the business of diplomacy and turns it into an amiable aside. The use of such collegial superlatives suggests someone taking great pains to soften a blow — not something the president is necessarily known for.

—I KNOW WHAT’S GOOD FOR YOU (PLUS SOME EPIC SWEEP). “(T)he Singapore summit, for the good of both parties, but to the detriment of the world, will not take place.” Lots of presumption there, for better or worse.

—I WON’T BACK DOWN. Lest the recipient think Trump might be trying to sweet-talk him, the middle of the letter has a sharp anchor embedded in it. “You talk of your nuclear capabilities, but ours are so massive and powerful that I pray to God they will never have to be used.”

Worth noting here: Western religion is not exactly welcome in North Korea, a secular state where Christians have long been persecuted.

—BUT MAYBE THERE’S A FUTURE FOR US AFTER ALL. In the statecraft equivalent of singing a karaoke rendition of “Didn’t We Almost Have It All,” Trump made sure to tell him that “some day, I look very much forward to meeting you.”

But he also said, most pivotally: “If you change your mind having to do with this most important summit, please do not hesitate to call me or write.” That’s a long ways from “Go away — I never want to see you again.”

The president concluded, in lament: “This missed opportunity is a truly sad moment in history.”

No one is suggesting that Thursday’s letter was anything but a combination of well-conceived tactics and well-planned strategy. But it certainly represents an innovative approach in the annals of leader-to-leader communication, at least in the modern era.

Now it just needs to be translated into Korean — with some curiosity along the way about how it might come out the other end.

And then we wait. Though if the North’s history is any indication, probably not for very long.

(AP)