North Korean leader Kim Jong-un spends his birthday in talks with Chinese President Xi Jinping

North Korean leader Kim Jong-un spent his 35th birthday in Beijing for talks with Xi Jinping just weeks ahead of his second planned meeting with US President Donald Trump – a move that analysts interpreted as an effort to undermine Washington’s confidence in international sanctions.

Kim began his four-day trip to China on Monday with a train journey, and arrived in the capital on Tuesday morning, which also marked his birthday, a more low-key affair in North Korea than the celebrations of his predecessors.

The birthdays of Kim’s father and grandfather are official public holidays in North Korea, but it does not hold any official events to celebrate the current leader’s birth.

His trip to China was made at the invitation of Chinese President Xi Jinping, according to both Chinese and North Korean state media.

Kim Jong-un takes train trip to China for talks with Xi Jinping

South Korean news agency Yonhap said Xi and Kim held talks for an hour, but Chinese state media did not disclose any details about the meeting, only confirming that Kim was in China.

Kim’s visit coincided with the latest round of trade talks between the US and China in Beijing, prompting suggestions that China may use North Korean denuclearisation as a card in the negotiations with Washington.

But Chinese Foreign Ministry spokesman Lu Kang insisted that Beijing would not use its influence over North Korea as leverage in trade talks with the US.

This is Kim’s fourth trip to China since his maiden visit in March last year.

He is accompanied by his wife Ri Sol-ju, as well many of the regime’s most senior officials including his right-hand man Kim Yong-chol and Foreign Minister Ri Su-yong, according to North Korean state media KCNA.

Daryl Kimball, executive director of the Washington-based Arms Control Association, said Kim would be seeking Chinese support and help with respect to the policy direction outlined in his New Year’s Day Address, while trying to strengthen Pyongyang’s position going into another possible summit with Trump.

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Reports suggest that the summit may be held in Hanoi, Bangkok or Hawaii.

“We are negotiating a location … It will be announced probably in the not-too-distant future,” Trump told reporters at the White House on Sunday.

Zhao Tong, a fellow at the Carnegie-Tsinghua Centre for Global Policy in Beijing, said that Kim’s visit may be intended to send a warning signal to Washington.

“This visit could send the message to Washington that North Korea can fare well even if the US continues the sanctions and North Korea can still achieve its goals by accepting the Chinese support. This may be aimed at undermining Washington's confidence in its coercive leverage against North Korea through economic sanctions,” Zhao said.

North Korean has long argued that the US must accept a phased and synchronised denuclearisation process, meaning that it must ease sanctions during the disarmament process rather than waiting for Pyongyang to complete the process.

China has long been a supporter of this “action-for-action” approach, which it believes will ensure stability in the Korean peninsula and neighbouring parts of China.

But Trump on Sunday insisted sanctions would remain “in full force” until he gets “positive” results.

“It may make Washington a little more nervous about the geostrategic implications of a closer DPRK-China ties as Washington may hate to see Beijing strengthening its regional influence over the Korean peninsula and beyond,” Zhao said.

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Sean King, a former US diplomat who is now senior vice-president of political strategy firm Park Strategies, said North Korea was using China as its security guarantee before the summit with Trump.

“North Korea has long used mainland China and its banks as a transit gateway and funding source for its many illicit businesses the world over … This way, Kim can be more confident up against Trump,” King said.

“If Kim is indeed going to meet Trump again, he obviously wants to check in with his chief enabler and patron, Xi, before stepping out on the world stage again.

“Kim will likely seek guarantees from Beijing that it will maintain its violations of sanctions against North Korea and keep its taps to Pyongyang flowing,” he said.

China remains North Korea’s closest ally and the 1961 Sino-North Korean Mutual Aid and Cooperation Friendship Treaty dictates that the two must undertake all necessary measures to oppose any country or coalition of countries that might attack either nation.

Kim, in his annual New Year’s Day speech, repeated his pledge to denuclearise the Korean peninsula – but only said he would not “make, test and spread” nuclear weapons in the future and did not make specific pledges concerning is existing nuclear arsenal.

He also proposed “multiparty negotiations” on replacing the armistice agreement that brought an end to the 1950-53 Korean war with a formal peace treaty.

“It is still not very likely that North Korea would make concessions such as providing a full list of its nuclear inventory, which could make its small nuclear arsenal more vulnerable to a US military strike,” Zhao said.

“As a rational strategy, Kim Jong-Un should want to play strategic balance between the two big powers in Northeast Asia: China and the United States.

“This would give Kim the best chance for achieving his goal of keeping a nuclear deterrent capability and having the economy develop simultaneously,” he added.

Cheong Seong-chang, a researcher at the Sejong Institute in Seoul, said Kim’s summit with Xi was expected to focus on denuclearisation of the Korean peninsula, the establishment of a peace regime to replace the current armistice and relief of sanctions against the North.

It cannot be ruled out that Kim and Xi will discuss shipping the North’s intercontinental ballistic missile out of the country to dismantle them, an issue that the US wanted to address, he added.

Additional reporting by Zhenhua Lu and Park Chan-kyong