BEIJING It was a relationship sealed over the most beautiful piece of chocolate cake you have ever seen.

After a day spent getting to know each other at his estate in Palm Beach, Fla., President Trump broke some major news to his Chinese counterpart over dessert. Fifty-nine Tomahawk missiles were locked, loaded and then launched toward Syria.

[U.S. strikes Syrian military airfield in first direct assault on Bashar al-Assads government]

In Trumps retelling, Xi Jinping was silent for 10 seconds, ominously asked for the comments to be translated a second time and finally declared he was okay with the idea. And so the Citrus Summit, as it has been nicknamed, was to be a success.

In short order, China has gone from an enemy and a threat, a job stealer and economic predator, to becoming a friend and partner of the new U.S. administration. In interviews with theFox Business Network and theWall Street Journal, Trump said he and Xi shared great chemistry, had formed an outstanding relationship, and understood each other.

(Jenny Starrs/The Washington Post)

All of a sudden, U.S. policy toward China seems broadly similar to that pursued by his predecessor. Trump might be a very different personality than President Barack Obama, the Global Times newspaper commented Friday, but there are many signs he is returning to Obamas diplomatic strategy.

Yet how deep is this newfound friendship with China, and how sustainable is the relationship?

If Trump has flipped once, could he flip again?

The answer to that question could lie in North Korea.

Just before the summit, Trump told the Financial Times that the Chinese were the world champions of currency manipulation. A few days after it, he told the Wall Street Journalthat China does not manipulate its currency.

Acartoon in Chinas Global Times on Friday mocked Trump as the Shifter-in-Chief, showing him at the wheel of a bus careening all over the road, but the overall mood is upbeat here at what state media are calling the big flip.

[A moderate catches Trumps ear]

The immediate effect of the two-day summit has been to bring an influx of tremendous dynamism into the complicated U.S.-China relationship, wrote thePeoples Daily, the Communist Party mouthpiece. This transition is a masterpiece of erudite political wisdom.

The erudite wisdom, one assumes, is supposed to be coming from the mouth of Chinas president, into the ear of the American one. Indeed, the Peoples Daily naturally chose aphotograph of Trump listening attentively to Xi speaking to adorn its post-summit front page.

Of course, it chosesimilar images in 2013, when Xi met Obama in Californias Sunnylands retreat and was again portrayed as the man delivering pearls of wisdom to his enraptured counterpart.

But this time there is real reason to believe that some of Xis arguments struck home, and not just in getting Trump to finally realize he was years out of date when it came to Chinas currency policy.

Just as no one could have imagined how complicated health care was, until you actually took the time to learn about it, Trump is fast learning the complications of tackling North Korea, thanks to some schooling from the Chinese president.

For months, the U.S. president had been firing off confident 140-character promises that he would solve the problem of Pyongyangs nuclear program, apparently believing that China could bring its neighbor to heel if it only wanted to. But Xi took the trouble to explain something about the history of China and Korea.

And after listening for 10 minutes I realized that its not so easy, Trump told the Journal. You know I felt pretty strongly that they have a tremendous power over North Korea. ... But its not what you would think.

This is not the first time Trump has changed tack. He questioned the one-China policy earlier this year before deciding to honor it, and has quietly dropped campaign threats to impose tariffs of up to 45 percent on Chinese goods.

Thats partly because he is learning as he goes along, sometimes slowly, sometimes painfully, always in full public view, experts say.

It is partly a function of the rise of the globalists within his administration, includingJared Kushner andGary Cohn, and the declining influence of the nationalists, such asStephen K. Bannon andPeter Navarro. But it is also a dawning of the realization that Trump needs a constructive relationship if he is to achieve his other foreign policy goals.

Ever since diplomatic ties with China were normalized nearly four decades ago, candidates have generally campaigned on being tough on China, before reverting to a more constructive approach while in office.

But if history is repeating itself, Trump represents an extreme case of the phenomenon.

For Bill Bishop, the publisher of theSinocism newsletter, there is a danger in making so many threats only to walk them back, and a missed opportunity to reexamine a policy approach that has brought more benefits to China than the United States.

The currency flip-flop made sense from an economic perspective, but one has to wonder how tough Beijing thinks Trump really is, and if Xi, a fan of Mao Zedong, sees Trump as yet another American paper tiger, he said.

It is too bad. America needs a new approach to dealing with the China challenge, one that is well thought out and strategically coherent. So far that does not appear to be happening, and that is good for Xi and the PRC [Peoples Republic of China] but not so good for the U.S.

Others take a different view.

President Richard Nixon is reported to have deliberately cultivated the Madman Theory, giving the impression he was irrational and volatile, and might even use nuclear weapons, in an attempt to scare the North Vietnamese and the Soviet Union. The credible threat of military action by the George W. Bush administration may have helped bring North Korea back to the negotiating table in 2006.

In a similar vein, Trumps decision to bomb Syria while hosting Xi was a shrewd move, some argue, helping to persuade Beijing to turn up the heat on its ally. In February, China announced it wascutting off coal imports from North Korea, severing an important economic lifeline for the regime, and has since reportedly turned back two coal shipments.

China does move on North Korea if they are sufficiently scared of the U.S., said Daniel Blumenthal of the American Enterprise Institute. They may pressure Kim if we keep the pressure on China.

Orville Schell, head of the center on U.S.-China relations at New York's Asia Society, said real world realities are beginning to bring Trumps policy closer to that of Obama, but the difference is Trumps utterly unpredictable nature, and his capacity to reverse course in a heartbeat.

Schell said this had put China somewhat off balance, uncertain if Trump might impose secondary sanctions or even launch a military strike on North Korea.

This kind of brinkmanship can be dangerous in diplomacy, but it could also get Beijing's attention and chasten Xi to make a deal before something untoward happens, Schell said.

Paul Gewirtz, director of the Paul Tsai China Center at Yale Law School, said China may impose tougher sanctions against North Korea, but not because Trump tells it to.

Those are likely to come from an ongoing assessment of Chinas interests and rising Chinese public opinion against North Korea, he said.

In the end, though, China and the United States have significantly different approaches to the issue of North Korea, and this fact alone remains a major challenge to the new rapport between Xi and Trump.

The evolution toward a more constructive relationship is certainly welcome, said Paul Haenle, director of the Carnegie-Tsinghua Center. But I think the big question is whether or not this can be sustained once the Chinese begin to underperform on trade or North Korea as times goes on. Will Trump be willin
g to confront his new friend Xi Jinping in order to defend U.S. interests?

Jin Xin, Luna Lin and Congcong Zhang contributed to this report.

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Chocolate cake and chemistry repair US-China ties. But will North Korea spoil the party? - Washington Post