“The Chinese side will communicate strategically with the South Korean side on Korean peninsula matters, and we will proceed together [with the South Koreans] for the progression of a diplomatic solution to the peninsula situation,” Kong said.

“The new year marks a historical starting point to the Korean peninsula situation,” he added, emphasising China’s role on the peninsula.

Senior North Korean official Kim Yong-chol reportedly bound for Washington to meet President Donald Trump

Lee, calling for Beijing’s support, said there was still “a long way to go” before peace could be achieved.

“South Korea and China need to work together closely to ensure the momentum of the dialogue continues to grow this year. We need to gather wisdom for the complete denuclearisation and permanent settlement of peace on the Korean peninsula,” he said.

Experts said the meeting suggested a diplomatic shift by Seoul to include China from the beginning of the peace process, after it appeared last year Beijing would be sidelined entirely from the negotiations.

In 2018, Washington and Seoul signalled they may proceed to the declaration of an official end to the Korean war without China’s involvement.

South Korean leader Moon Jae-in last year indicated his support for a trilateral summit with US President Donald Trump and North Korea’s Kim Jong-un if their talks led to progress on an end-of-war declaration.

But that plan was never realised, and ties between Beijing and Pyongyang have continued to develop, with four visits to Beijing by Kim since March.

The cooperation between Beijing and Seoul, which wants to reignite economic projects with the North, may pressure Washington to adapt its approach.

Zhang Baohui, professor of political science and director of the Centre for Asian-Pacific Studies at Lingnan University in Hong Kong, said Seoul may be seeking China’s help in accelerating the denuclearisation deal.

“South Korea is anxious that the denuclearisation process has stalled and that achievements on the peacemaking side of Moon’s North Korea policy may be reversed,” he said.

“It is possible that both China and South Korea may want the US to be more flexible on that issue. China and South Korea are more sympathetic toward North Korea’s action-for-action approach for denuclearisation.”

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

Ryo Hinata-Yamaguchi, a visiting professor at Pusan National University in South Korea and adjunct fellow at the Pacific Forum, said: “China definitely would want to be relevant and ensure the denuclearisation process was not centred on the US and Republic of Korea.”

Chinese President Xi Jinping, during his summit with Kim in Beijing last week, said China was ready to play “a positive and constructive role in maintaining peace and stability,” and emphasised his country’s role in the Korean peninsula.

Meanwhile, on Thursday, North Korea’s Kim Yong-chol, vice-chairman of the ruling Workers' Party Central Committee, left for the US capital after transferring in Beijing.

Kim, Pyongyang's former spy chief, is regarded as US Secretary of State Mike Pompeo’s North Korean counterpart has been the country’s leading negotiator in the nuclear talks with the US.

His visit to the US, where he may meet with Pompeo, comes as plans are underway for a second Trump-Kim summit, possibly in Vietnam.