By Josh Chin and Andrew Jeong 

BEIJING -- With denuclearization talks between Pyongyang and Washington at a standstill, North Korean leader Kim Jong Un turned this week to his country's longtime patron, China.

For months, North Korea has demanded the U.S. ease sanctions, claiming to have dismantled some of its nuclear facilities. Washington has refused to budge, pledging to maintain sanctions until Pyongyang's complete denuclearization in accordance with the agreement between President Trump and Mr. Kim in Singapore last year.

Mr. Kim's arrival in Beijing on Tuesday at Chinese President Xi Jinping's invitation offered a reminder of the close ties between North Korea and China, whose actions have been essential to the U.S.-led effort to enforce sanctions on Pyongyang. That has given President Xi leverage in China's dealings with Washington, with whom relations have deteriorated as their trade dispute has unfolded.

The timing of the Xi-Kim meeting -- as U.S. and Chinese negotiators held their latest round of trade talks in Beijing -- represents a "coincidence of interest" between North Korea and China, said Steve Tsang, director of the SOAS China Institute in London. Back in 2017, when Pyongyang was testing long-range nuclear missiles, the U.S. and its allies looked to Beijing to help broker a solution.

Now, Beijing could see North Korea as leverage in its trade dispute with the U.S., while Pyongyang needs China's assistance securing a second summit with Mr. Trump.

"It's in Beijing's interest to remind the U.S. they can be very helpful on North Korea," Mr. Tsang said. "It's a message from both Beijing and Pyongyang to Washington."

This year marks the 70th anniversary of the establishment of diplomatic relations between China and North Korea. On Tuesday, which was also Mr. Kim's birthday, Chinese state-run media ran comments by experts extolling China's role in finding a solution to the nuclear issue.

"Kim Jong Un's willingness in 2018 to walk the path to denuclearization and meet with the U.S. stems in large part from his trust in China," the Global Times quoted Wang Sheng, a North Korea expert at Jilin University in northeastern China, as saying.

Mr. Kim appeared to have arrived in Beijing on Tuesday morning by train. He traveled with his wife and senior officials, and plans to stay in China until Thursday, official North Korean and Chinese news agencies reported.

Chinese Foreign Ministry spokesman Lu Kang said at a regular press briefing on Tuesday that Mr. Kim's visit aimed to strengthen communication between the two countries and that China also encourages communication between North Korea and the U.S. He denied any connection with U.S. trade talks.

"You would know that China's diplomacy is rich and colorful, and we have many major diplomatic engagements," Mr. Lu said. "There's nothing particularly unusual for some diplomatic engagements to coincide."

China has long been North Korea's top economic partner and de facto security guarantor. Beijing sent hundreds of thousands of troops to aid North Korea during the 1950-53 Korean War.

Security analysts said Mr. Kim's mission in Beijing was likely to seek Mr. Xi's support for his approach in the nuclear talks with the U.S., and to press China to ease sanctions pressure.

"Kim Jong Un is asking Xi to give him the leverage to say 'no' to U.S. demands to permit inspection of North Korea's nuclear facilities," said Nam Sung-wook, a former South Korean intelligence official. "That leverage is breathing room from sanctions."

Choi Kang, vice president of research at the Asan Institute for Policy Studies, a private think tank in Seoul, said Mr. Kim could be hoping to secure a Chinese agreement to provide the North with more energy aid.

"It's going to be difficult for Beijing to publicly announce energy support to Pyongyang, due to sanctions," said Mr. Choi. "But the Chinese are already doing it furtively," he added, referring to suspicions allegations that China has been providing North Korea with oil through ship-to-ship transfers on the high seas.

A U.S. congressional commission report said in November that China appeared to have relaxed enforcement of sanctions on North Korea and was "undermining the U.S. 'maximum pressure' campaign."

Beijing has said it enforces sanctions in accordance with United Nations Security Council resolutions.

Despite historic ties between their countries, Mr. Kim didn't visit China for the first six years of his rule after succeeding his father, Kim Jong Il. But having met Mr. Trump, Mr. Kim now enjoys new diplomatic clout, said John Delury, an expert in China and North Korea at Yonsei University in Seoul.

On the flip side, he said, Mr. Xi and other Communist Party leaders now have to work harder to make sure Pyongyang doesn't decide to deal directly with the U.S. and cut China out of the nuclear conversation.

Mr. Delury said Mr. Xi has an interest in linking North Korea with trade, because it allows Beijing to portray itself as doing Mr. Trump a favor by helping him notch a foreign-policy win.

"If it's those two issues and if the focus is on North Korea, then it takes a lot of pressure off China across the board," he said.

Meanwhile, speculation has grown around the timing and venue for a second U.S.-North Korea summit. Last year, Mr. Kim went to China for talks with Mr. Xi about a month before the North Korean leader's June meeting with President Trump. He followed up with another visit to Beijing a week after its conclusion.

South Korea's semiofficial Yonhap News Agency reported on Tuesday that Vietnamese officials had alerted North Korea of their desire to host the next U.S.-North Korea summit. The report mentioned Vietnam's port city of Da Nang as a possible location. The city hosted a major Asia-Pacific summit in 2017, which Mr. Trump attended, and a U.S. carrier docked there last year.

A U.S. State Department official declined to comment, citing reduced staffing amid the U.S. government shutdown.

"Vietnam is one of the best places," said Mr. Nam, the former intelligence official. But the problem isn't where to hold the summit, he added, but rather the need to reach specific denuclearization agreements before the two leaders meet.

"If Trump and Kim agree to weak agreements again, it'll be bad for both of them. Kim Jong Un won't have his sanctions lifted," Mr. Nam said.

--Chun Han Wong in Beijing and Timothy W. Martin in Seoul contributed to this article.

(END) Dow Jones Newswires

January 08, 2019 09:30 ET (14:30 GMT)

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