Donald Trump is a brash reality-television-star-turned-president billionaire. South Korea’s Moon Jae-in is a former human-rights lawyer and activist who spent time in jail in his fight against official corruption. President Trump’s administration faces a growing swirl of investigations; President Moon was elected to restore trust after his predecessor went to jail for bribery and influence-peddling.

That’s not to say the US and Korean leaders don’t have lots to discuss in Seoul in the days ahead. But with worldviews every bit as a divergent as their personal stories, humankind should tamp down expectations of anything notable happening.

Moon and Trump will do more dancing around than negotiating on the three big issues driving their agendas apart: North Korea, trade and China.

Differences over Kim Jong-un’s provocations are well known. Moon wants to talk, resurrecting former President Kim Dae-jung’s “sunshine policy.” Trump is in Twitter-troll mode, threatening “fire and fury” and scaring Seoul with “calm before the storm” teasers like some TV producer juicing up ratings.

Less well known is how Trump’s White House has left Moon’s administration hanging. Seoul’s decision to host US-designed Terminal High Altitude Area Defense (THAAD) systems enraged China’s Xi Jinping. Xi’s government has spent the last several months retaliating: cancelling tour groups, causing visa troubles for K-pop performers, shuttering Lotte stories and orchestrating other hits to commercial interests that Hyundai Research Institute says will cost Korea about US$8 billion this year. All the while, Trump’s White House has been disturbingly silent.

That’s unfortunate, considering Seoul is taking hits partly for Washington. Yes, installing THAAD systems is about keeping 50 million South Koreans safe. But it’s also about having America’s back in North Asia as Kim’s missiles expand their reach. Other White Houses would be sure to make Seoul’s cooperation worth its while. Instead, Trump is scrapping a five-year old Korea-US free trade pact, or KORUS.

Negotiations on KORUS began under President George W. Bush and got ratified by Barack Obama in 2012. Now it’s in limbo as Trump pushes to renegotiate. It’s of a piece with his passion for reneging on deals: Trans-Pacific Partnership, Paris climate change pact, the Iran nuclear agreement, you name it.

Just as with Shinzo Abe’s Japan, Trump thinks Moon’s people are taking advantage of America. “We’re getting destroyed in Korea,” Trump said in April. He’s also called it a “horrible deal. It was a Hillary Clinton disaster, a deal that should’ve never been made.” Given Trump’s belief that KORUS is a “one-way street,” how could Moon expect Asia’s No. 4 economy to emerge from any renegotiation unscathed? The best-case scenario is for Moon to turn on the charm and make Trump’s visit as quick and painless as possible.

Finally, there’s China. After nine-plus months of Trumpian chaos, most Asian leaders are hoping January 2021 comes quickly – and unpreceded by major calamity. A new wrinkle, though, is that Xi just extended Moon an olive branch. Beijing and Seoul just agreed to move beyond the THAAD spat, news that boosted South Korean stocks.

Xi’s people also are talking with Moon’s about a meeting in Beijing by year end. China may have engineered this as a slight aimed at Prime Minister Abe, which in turn could open the door for a possible Xi visit to Japan. That might be an opportunity to increase trade flows with Asia’s biggest economy as Trump tightens the vice from the other direction.

China will necessitate quite the balancing act from Moon and Trump, who will fly directly from Seoul to Beijing on Wednesday. But he’d be wise to shore up the US-Korea alliance first.

Moon’s strategy appears to be flattery: Trump will be lavished with the first state visit for a US leader in 25 years, full military honors, National Assembly speech, gala dinner, cultural performances.

Trump would be wise to return the favor. He will find in the months (and perhaps years) ahead that Washington needs Seoul just as much as Seoul needs Washington.