Kim's third trip to China since March comes as Beijing tries to strengthen role as mediator between US, N Korea.
Beijing: North Korean leader Kim Jong Un briefed Chinese President Xi Jinping on Tuesday on his historic summit with US President Donald Trump, a visit that underscores Beijing's efforts to remain at the centre of fast-moving nuclear diplomacy.
Kim's third trip to China since March comes as Beijing tries to strengthen its role as a mediator between the US and its neighbour, where it claims compelling security and economic interests.
The North's leader, who is believed to have landed in the Chinese capital Tuesday morning, met Xi at the ornate Great Hall of the People. He was given a full ceremonial welcome, including a military revue and a gaggle of adoring children shouting out welcomes.
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Kim "felt thanks for and highly praised China's promotion of denuclearisation of the Korean Peninsula and its important role in protecting the peninsula's peace and stability," state-run CCTV said.
North Korea "hopes to work with China and other concerned parties to promote and establish a solid, long-lasting peace mechanism on the Korean Peninsula and make joint efforts to achieve a lasting peace on the peninsula."
For his part, Xi told Kim he "wants North Korea and the US to carry out the results of their leadership summit" in Singapore on June 12, the report said.
Trump and Kim pledged in a joint summit statement to "work toward the complete denuclearisation of the Korean Peninsula".
The United States relies on China to enforce UN economic sanctions against the North, giving Beijing potential leverage in its looming trade war with Washington.
"I think that North Korea can be another card Beijing can play to win leverage in negotiations with Washington," Yang Moo-jin, professor at the University of North Korean Studies in Seoul, told AFP.
In addition to discussing last week's Singapore summit, Kim was expected to ask China for help in easing the sanctions in return for his pledge to denuclearise, according to Wang Dong, an international relations expert at Peking University.
"The Chinese and North Korean leaders are carrying out consultations on how to jointly move the Korean nuclear issue forward," Wang said.
Following the Singapore summit, China suggested the UN Security Council could consider easing the economic restrictions on its Cold War-era ally.
China may not have been at the table for the summit in Singapore but it retains strong influence behind the scenes, Wang said.
Tuesday's visit shows that China is "key" to the talks, the analyst added. "It reflects that China is indispensable to the entire Korean nuclear issue."
- 'Differences ahead' -
Trump had hailed Kim's denuclearisation pledge as a concession. But critics said the stock phrase long used by Pyongyang stopped short of longstanding US demands for North Korea to give up its atomic arsenal in a "verifiable" and "irreversible" way.
It was urgent for Xi and Kim to discuss how North Korea will work towards meeting US demands, said Beijing-based international relations commentator Hua Po.
"There may be differences ahead between the DPRK (North Korea) and the US in regards to denuclearisation, because the US wants irreversible and verifiable denuclearisation. It may be difficult for Kim Jong Un to accept," Hua told AFP.
"Therefore, both China and the DPRK want to strengthen communication and form an overall strategy to deal with the United States going forward," Hua added.
In return for the denuclearisation pledge, Trump made the shock announcement that he would stop joint military drills with South Korea, long seen as a provocation by Pyongyang and Beijing.
Analysts saw this as a clear sign of Beijing's influence.
Beijing has repeatedly called for a "suspension for suspension" approach, under which the North would stop its nuclear and missile tests in exchange for the US and South Korea halting military exercises.
Washington previously rebuffed the proposal. But on Tuesday the US and South Korean militaries confirmed they have called off a major joint exercise following Trump's order.
Kim will be in Beijing through Wednesday, state media reported.
His two previous trips to China, including his maiden official voyage abroad in March, had been kept secret until he returned home.
"I think that China convinced North Korea that high-profile trips like this can no longer be kept secret for so long," said Yang, the Seoul analyst.
"Also Kim Jong Un is seeking to establish this image as a normal leader of a normal country in the international community."