BEIJING — In the sudden rush of diplomacy involving North Korea, China has appeared to have the upper hand, hosting the North Korean leader, Kim Jong-un, twice before his long-anticipated Singapore summit meeting with President Trump even begins.

Yet as Mr. Kim prepares to finally meet Mr. Trump in Singapore on Tuesday, some analysts say Beijing appears to be getting a sudden case of the jitters.

They say the Chinese leaders, who are unused to being on the outside looking in, are growing anxious about whether they can keep their Cold War-era ally firmly in its current orbit around China. Leaders in Beijing are worried, experts say, that Mr. Kim might try to counterbalance China’s influence by embracing the United States, North Korea’s longtime enemy.

According to analysts, Mr. Kim may seek to do this by offering Mr. Trump some sort of deal, which would probably include some pledge to scrap his nuclear arsenal in exchange for American help to reduce or even eliminate North Korea’s near total dependence on China.

“If you look at history, North Korea is not sure of China, and has a kind of revenge mentality,” said Shen Zhihua, a prominent Chinese historian on North Korea. “The worst outcome is that the United States, South Korea and North Korea all get together and China gets knocked out.”

Analysts said China worried that the United States could also use the Singapore meeting to engineer a united Korean Peninsula that joins the North with South Korea, one of Washington’s closest allies. For China, that raises the uncomfortable specter of American troops on China’s doorstep, erasing North Korea’s traditional role as a buffer.

There is even the remote possibility that North Korea could flip allegiances, just as China did in 1972. When President Richard Nixon visited Beijing that year, Mao Zedong further distanced China from the Soviet Union in favor of friendship with the United States.

Some analysts ask whether the United States could now flip North Korea to its side and away from China.

“China can see some shocking resemblance to Nixon coming to China with Trump and North Korea,” said Yun Sun, a China analyst at the Washington-based Stimson Center. “If China could do it, why not North Korea?”

Experts say the more preferable outcome for China would be for Mr. Trump and Mr. Kim to sign a peace treaty that formally ends the Korean War and paves the way for the eventual withdrawal of the 28,500 American troops in South Korea.

That would leave the entire peninsula open to China’s influence, while eroding the confidence of American allies in Asia regarding Washington’s commitment to the region.

Either way, a strategic realignment in Northeast Asia appears underway, with North Korea apparently intent on preserving its independence from China, and China not wanting to lose its leverage over the North and its young leader.

There have already been signs that Mr. Kim is bridling under China’s influence.

In one of his first acts after taking power in 2011, Mr. Kim ordered the killing of his uncle Jang Song-thaek, who had been seen as China’s main conduit to Pyongyang; Mr. Kim later ordered the killing of Kim Jong-nam, his half brother, who was also friendly to China, according to American and South Korean intelligence agencies.

During his first six years of rule, Mr. Kim kept China at arm’s length, not even meeting with China’s leader, Xi Jinping. He finally met Mr. Xi in Beijing in March and then again in the Chinese port city of Dalian in May as part of the gamesmanship before his landmark meeting with Mr. Trump.

What went on in those two meetings in China remains shrouded in secrecy. Chinese experts speculate that Mr. Xi promised hefty financial help or security guarantees.

Some Chinese analysts also note a long-simmering resentment in North Korea about being considered the little brother of its much bigger neighbor. They said this touchiness was apparent in the lack of monuments in North Korea honoring the estimated 400,000 Chinese soldiers who died helping protect the North during the 1950-53 Korean War.

Still, the odds of North Korea shifting its allegiance toward the United States are not great, Western experts say. That is particularly true in the era of President Trump, who is seen as an uncertain partner even for Washington’s existing Asian allies.

“North Korea has no reason to believe that the U.S. would be willing or able to defend it from China,” said Hugh White, an Australian defense strategist. “Who in Pyongyang would believe that America could fight and win a land war against China on China’s borders?”

Rather, Mr. Kim is more likely to be looking for ways to increase his level of independence from China, a desire that has recently been shown by a meeting with the Russian foreign minister, Sergey V. Lavrov, and by reports that the Syrian leader, Bashar al-Assad, is planning to visit Pyongyang.

“Like any middle power, Kim is aiming to be independent of any great power — both China and America — and he is already a fair way towards that goal,” Mr. White said. “That’s what the nukes are for. What Kim wants is to keep as much of his independence as possible and hence as much of his nuclear capability as possible.”

For Mr. Kim, an embrace of the United States would also have its limits.

Although Mr. Trump has chosen largely to ignore the human rights abuses in North Korea, there is still enormous hostility in Washington toward what remains a Communist dictatorship. Some members of Congress and of Mr. Trump’s administration, including his national security adviser, John R. Bolton, have advocated regime change in the North.

Mr. Kim would also have little reason to expect economic help from the United States. After North Korea’s second-most powerful figure, Kim Yong-chol, visited him in the Oval Office, Mr. Trump said he had no intention of helping the North build its backward economy, a job that he said belonged to China and South Korea. “That’s their neighborhood,” Mr. Trump said.

Already, trade across China’s border with North Korea is stepping up. Last week, the state airline, Air China, renewed flights to Pyongyang after a six-month hiatus.

China, which reluctantly enforced United Nations sanctions at the urging of Mr. Trump, is now anxious to mend ties with the North by helping with its economy, said Cheng Xiaohe, a North Korea expert at Renmin University of China.

“The United States and China are moving away from the uneasy cooperation on North Korea of last year,” Mr. Cheng said. “China doesn’t trust Trump, and the U.S. doesn’t trust China.”

Still, Beijing’s past efforts to help build the North’s economy have often ended in misery for Chinese companies, making them leery of new investments.

Chinese investors in coal mines and other natural resource ventures have complained of being duped by the North Koreans, and then having no legal protection. A major bridge built by the Chinese over the Yalu River between the border town of Dandong and North Korea after Premier Wen Jiabao visited Pyongyang in 2009 remains unfinished. The North has refused to connect the road on its side of the river.

No senior Chinese officials are expected to be in Singapore during the Trump-Kim summit meeting. China will have to wait to hear what happened from the American secretary of state, Mike Pompeo, who is planning to travel to the South Korean capital, Seoul, and to Tokyo before going to Beijing to give briefings about the meeting’s results.

Apparently eager to maintain China’s own diplomatic momentum, Mr. Xi has accepted an invitation from Mr. Kim to visit North Korea. He could go as soon as the end of this month, some analysts suggest.

“It would be natural to expect Xi to make his first visit as president to Pyongyang in the not-too-distant future,” said John Delury, an associate professor of Chinese Studies at Yonsei University in South Korea.

The visit would be part of Mr. Kim’s careful post-Singapore strategy, a move to show that he was his own man, a creature of neither the United States nor China.

“Kim seems to be pursuing a rebalancing of dynamics, rather than an out-and-out ‘defection’ to the U.S. side,” Mr. Delury said.

Jane Perlez

---