Just days after he stood outside the White House and announced the planned meet between the US president and North Korean leader, Chung Eui-yong was in Beijing to brief China's top diplomat Yang Jiechi on the fast-moving efforts to address the nuclear standoff.

Trump and Kim have agreed to meet by the end of May, although they have yet to confirm a date or time.

"Our president, Moon Jae-in, and the (South Korean) government believe that various advances toward achieving the goal of peace and denuclearisation of the Korean peninsula were made with active support and contribution from President Xi Jinping and the Chinese government," Chung said.

Yang touted the "positive changes" on the Korean peninsula.

"We will continue to realise the goal of denuclearisation, uphold the peaceful unification of the peninsula, and solve problems through dialogue and consultation," he said.

China has long urged the US and North Korea to start bilateral talks about Pyongyang's nuclear weapons programme.

Beijing has played a key role in passing and implementing UN sanctions on the North, which are believed to have put immense pressure on the country's fragile economy.

China is North Korea's only diplomatic ally and its most important trade partner.

Still, some in China are afraid the country, which hosted failed six-nation talks on the nuclear issue a decade ago, could be cut out of negotiations on denuclearising the Korean peninsula.

Chung will meet with other top leadership in Beijing Monday before heading to Russia later in the week.