Trump is expected to demand that China curtail its dealings with Pyongyang and expel North Korean workers. Trump has praised China for taking some steps against Pyongyang but urged them to do more, as administration officials believe the border between China and North Korea remains a trade corridor.

"I want to just say that President Xi -- where we will be tomorrow, China -- has been very helpful. We'll find out how helpful soon,'' Trump said Tuesday night in Seoul. "But he really has been very, very helpful. So China is out trying very hard to solve the problem with North Korea.''

The White House is banking on Trump's personal rapport with Xi to drive the negotiations. Trump has frequently showered praise on Xi, who recently became the nation's most powerful leader in decades, including with a trip to Trump's Florida estate for a summit.

"He's a powerful man. I happen to think he's a very good person. Now with that being said, he represents China, I represent the U.S.A., so, you know, there's going to always be conflict,'' Trump recently told the Fox Business Network. "People say we have the best relationship of any president-president, because he's called president also. Now some people might call him the king of China. But he's called president.''

The president and first lady Melania Trump were greeted at the airport by dozens of children who waved U.S. and Chinese flags and jumped up and down. They sipped tea with Xi and his wife, Peng Liyuan, received a private tour of the Forbidden City, Beijing's ancient imperial palace, including a performance by young opera students before dinner. Trump said afterward that he's "having a great time'' in China.

White House officials point to the summit in Florida this spring, an event partly defined by Trump telling his Chinese counterpart about the missile strike he ordered on Syria while the two men dined on chocolate cake. But experts in the region suggest that Xi may be playing Trump.

"Trump keeps portraying his relationship with XI as great pals but that's wildly naive,'' said Mike Chinoy, an expert on East Asia policy at the U.S.-China Institute at the University of Southern California. "The Chinese have figured out how to play Trump: flatter him. And there's nothing the Chinese do better than wow foreign diplomats.''

Trump talked tough during his campaign about fixing American's trade relationship with China and labeling it a ``currency manipulator.'' But he has signaled that he would take it easy on Beijing if it will help with the nuclear threat from North Korea.

"Trump has mortgaged the whole U.S.-China relationship to get the Chinese on board with the North Korea plan,'' Chinoy said. ``He is now coming at it from a position of weakness.''

White House officials have said that if Trump were to chide Xi about human rights or democratic reforms he would likely do it privately. Andrew Nathan, a political science professor and China expert at Columbia University, said Trump's ``infatuation'' with Xi was reminiscent of former Secretary of State Henry Kissinger's fascination with Zhou Enlai, the first Premier of the People's Republic of China.

"For Trump, Xi is wish fulfillment: `I wish I could be as powerful as that guy!''' Nathan said.

One uncertainty for Trump: whether he will be able to use Twitter in China, which has banned the social media platform. Though the United States could enable it to work, the White House declined to comment on whether Trump would tweet from China.

Trump arrived in Beijing after two days in Seoul, where he largely avoided the inflammatory rhetoric _ like dubbing North Korean dictator Kim Jong Un "Little Rocket Man'' _ that has defined his approach to Pyongyang. But he also warned North Korea in his speech to ``not underestimate us. And do not try us.''

He also sounded an optimistic note while in South Korea, saying confidently, if vaguely, that ``ultimately, it'll all work out'' while shifting views and expressing hope that diplomacy could resolve the tensions. Trump also underlined U.S. military options, noting that three aircraft carrier groups and a nuclear submarine had been deployed to the region.

But he said "we hope to God we never have to use'' the arsenal.

One hoped-for message to Pyongyang went unsent. Though the White House had previously indicated that Trump would not visit the heavily fortified demilitarized zone separating North and South Korea, plans had been in the works for him to make an unannounced visit Wednesday morning.

Trump boarded the Marine One helicopter and flew to within five minutes of the DMZ when U.S. military pilots and Secret Service agents determined the fog was too thick to safely land. The helicopter returned to Seoul and Trump waited nearly an hour for the weather to clear.

The fog did not lift in time. (AP)