Beijing: China has passed the baton to a younger generation to solve the world's most intractable diplomatic dilemma - North Korea.

Kong Xuanyou, 58, quietly took over from the 71-year-old Wu Dawei as China's special envoy on North Korea at the start of August.

Mr Kong is ethnically Korean, speaks Korean, and has been tasked with leading China's efforts to restart six-party talks on North Korea's nuclear and missile program.

The career diplomat and assistant foreign minister is also fluent in Japanese, and is a former ambassador to Vietnam.

Mr Wu, who spent 13 years in the role, was at one time described as "the most incompetent official in China" by the South Korean government, according to a Wikileaks cable.

The 2010 US cable reported that South Korea's then vice foreign minister Chun Yung-woo believed Mr Wu only retained his position as China's lead negotiator after North Korean lobbying, and this was "a very bad thing".

Mr Chun described a "generational difference in Chinese attitudes towards North Korea", with the younger generation of officials ready to face the reality that North Korea had little value to China as a buffer state.

Mr Wu, by contrast, was an "arrogant, Marxist spouting former Red Guard who 'knows nothing about North Korea, nothing about non-proliferation'," the Wikileaks cable quotes Mr Chun as saying.

Mr Kong's appointment appears to coincide with China's support in the United Nations Security Council for tougher sanctions against North Korea.

Korean media, which broke the news of Mr Wu's replacement a week ago, have speculated that with the US special envoy on North Korea, Joseph Yun, also ethnically Korean, negotiations over North Korea's weapons program could be conducted in the Korean language.

The Chinese government confirmed Mr Kong's appointment and Mr Wu's retirement on Monday. A spokeswoman denied any link to the "current developments" on North Korea.

Mr Kong was part of the Chinese negotiating team during the six-party talks with North Korea, which ran from 2003 to 2008, and also involved the US, Russia, South Korea and Japan.

Mr Wu was reportedly snubbed by Pyongyang in April, which refused his request to meet amid a flurry of shuttle diplomacy between China, South Korea and the US amid an acceleration of North Korean missile tests.

Mr Kong had sat alongside Chinese Foreign Minister Wang Yi when a North Korean envoy made the first visit to Beijing in nine months in March. This came days after China stopped buying coal from North Korea.

China said it would impose the new sanctions on North Korean iron ore, coal, lead and seafood from Tuesday.

The chairman of the United States Joint Chiefs of Staff, General Joe Dunford, met with his Chinese counterpart General Fang Fenghui in Beijing.

The US military described the visit as part of the United States' "diplomatic and economic campaign to deter North Korea". It has been speculated in Chinese media that General Dunford is outlining potential military options against North Korea.

General Dunford said the meeting would "continue to develop our military-to-military relationships, to mitigate the risk of miscalculation in the region and to have cooperation where those opportunities exist."

North Korean leader Kim Jong-un met with his military leaders to discuss a plan to fire missiles into the waters off Guam, but held off making any decision and called for the US to stop provoking North Korea, North Korean media reported.

A day after General Dunford's visit to Seoul, South Korean President Moon Jae-in said no military action was possible in Korea without Seoul's consent.

"The government will prevent a war at all cost," said Mr Moon, vowing to step up diplomatic efforts.