BEIJING » The last known face-to-face contact between Kim Jong Un, the North Korean leader, and senior Chinese officials did not end well.

A member of China’s Politburo, Li Jianguo, led a small delegation to Pyongyang, North Korea’s capital, in November. He carried a letter from China’s new leader, Xi Jinping, which is said to have contained a simple message: Do not launch a ballistic missile.

Twelve days later, Kim did just that.

The relationship between North Korea and China, extolled in the past to be as close as "lips and teeth," has faltered ever since as Kim, a political neophyte believed to be in his late 20s, has continued to defy Xi, a 59-year-old seasoned statesman.

How far the alliance between the powerhouse China and the impoverished North Korea has soured is now debated openly in the Chinese news media. Few call it a serious rift, though a spirited debate appears to be underway within the Chinese government over how to handle Kim.

But with Secretary of State John Kerry in China this weekend on his first visit as the United States’ chief diplomat, some things are clear.

The personal relationships among Kim and his Chinese counterparts appear to be less familiar than when his father, Kim Jong Il, was in charge. Analysts suggest that could be a result of the significant age differences between the inexperienced Kim and the much older Chinese leaders.

There has been no publicized visit of Chinese leaders to North Korea since the embarrassing trip in November when Kim thumbed his nose at Xi’s request for restraint.

As relations frayed after Kim carried out North Korea’s third nuclear test in February, China suggested sending several senior officials to Pyongyang, including Dai Bingguo, a state councilor and experienced North Korea hand who retired in March, Chinese analysts said.

But Kim rebuffed the overture, the analysts said, a sign that the Chinese interpreted as the new leader wanting to show he is less dependent on Beijing than his father.

It not clear whether Xi has ever met Kim.

Xi last visited Pyongyang in June 2008 when he was vice president. He arrived before Kim Jong Il had a stroke, a period when the succession process that led to the appointment of Kim Jong Un as president had not yet begun.

Speculation mounted in 2010 and 2011 that Kim would replace his ailing father after the son was reported to have participated in one or more of the four official North Korean delegations to China in those years, a period when the Chinese were encouraging North Korea to open up its economy.

On at least one of those trips, Kim Jong Il did meet with Xi, who at that time was vice president, said John Delury, associate professor of East Asian studies at Yonsei University in Seoul, South Korea.

"However, there was never evidence Kim Jong Un did in fact go with his dad," Delury said. "I assume he did not, until there is positive evidence."

In August 2012, Kim’s uncle by marriage, Jang Song Thaek, a four-star general who is considered a close adviser to the new leader, visited Beijing and met with the Chinese leaders at the time, President Hu Jintao and Prime Minister Wen Jiabao.

It was assumed that Jang was setting the stage for a visit to China by the new, young leader, an idea that the Chinese appeared to be pushing as a way of showing what promise economic overhaul held for the repressed North Korea. Little came of the visit.

In the Chinese news media, Kim is getting a mixed reception. The state-run news media here have stopped short of calling Kim unflattering names, as they did when they labeled President George W. Bush "Little Mr. Bush."

In contrast, China’s social media sites have unleashed waves of satirical jokes, images and names aimed at Kim, who is often described in disparaging terms by ordinary Chinese.

China often censors comments on the Internet that run counter to Communist Party policy or are too critical of foreign policy. The barbs against Kim have been left intact.

A common description of Kim on social media sites is "The Kid." Another favorite: "Fatty, the Third."

That is a reference to the portly men who have made up the Kim dynasty: the founder of the state, Kim Il Sung, whose birth on April 15, 1912, will be celebrated Monday; his son, Kim Jong Il, who died in December 2011 after ruling the country since 1994; and his son, the current leader, Kim Jong Un. Their girth stands in contrast to the fact that much of the North Korean population struggles to get enough to eat.

In China’s state-run news media, the once-generous coverage of the North has become less tolerant. Some commentators called North Korea’s announcement that it would restart its Yongbyon nuclear reactor as "out of control" and "crazy."

A fairly stern editorial in Global Times on the eve of Kerry’s visit Saturday suggested there was a limit to China’s forbearance. "When Pyongyang’s acts seriously violate China’s interests, we will by no means indulge it," the editorial said.

The People’s Daily online edition on Thursday urged North Korea not to "misjudge the situation," and criticized the government for violating U.N. resolutions against nuclear testing and the launching of ballistic missiles.

The less favorable news media coverage of North Korea is also accompanied with tough words for the United States. "Do not add fuel to the flames," People’s Daily said, a reference to the sending this month of nuclear capable B-52 and B-2 bombers by the Obama administration as a show of support for the U.S. ally, South Korea.