China called  Wednesday for North Korea and the United States to go ahead with their historic summit as planned after Pyongyang threatened to pull out of the scheduled meeting between President Donald Trump and Kim Jong Un.

The North also cancelled high-level talks due Wednesday with Seoul because of US-South Korean military air exercises, denouncing the drills as a "rude and wicked provocation".

"The situation on the peninsula has eased up, which is worth cherishing," Chinese foreign ministry spokesman Lu Kang told a regular briefing.

"We hope... some of the high-level meetings that (the two sides) have been working towards can be held smoothly and... results can be achieved," Lu said.

"Only in this way can the easing up of the peninsula be consolidated, contributing to peace and stability in the region."

North Korea threatened to withdraw from the June 12 summit in Singapore if Washington seeks to push it into unilaterally giving up its nuclear arsenal.

"If the US is trying to drive us into a corner to force our unilateral nuclear abandonment, we will no longer be interested in such dialogue," first vice foreign minister Kim Kye Gwan said in a statement carried by state media.

Lu called for all parties to "avoid mutual provocations and further tension, so that they can jointly provide the necessary conditions and atmosphere for a political settlement of the peninsula issue through dialogue."

Chinese President Xi Jinping has met Kim twice over the last two months, as Beijing warms to its Cold War-era ally following a chill in relations.

In a sign of the improved relationship, a North Korean delegation is visiting Beijing to learn about China's experience in economic reform and opening up.

Xi Wednesday hosted a meeting with its leader Pak Thae Song, vice-chairman of the Central Committee of the Workers' Party of Korea, the North's ruling party.

Xi told Pak that China supports Kim's leadership and backs dialogue between Pyongyang and Washington, the official Xinhua news agency said.

Pak said his party was interested in learning from China's economic development and "reform and opening up" experience, the agency reported.  (AFP)