US Secretary of State John Kerry heads to Beijing on Saturday seeking China's help to rein in a belligerent North Korea and provide a foundation for Seoul to lower soaring tensions with Pyongyang.
Kerry was due to fly to the Chinese capital from South Korea where he held talks Friday with President Park Geun-Hye and offered public US support to her plans for initiating some trust-building with the North.
The Korean peninsula has been engulfed by escalating military tensions and dire threats of nuclear war ever since North Korea conducted a rocket test last December and a nuclear test in February.
Despite intelligence reports that the North has prepared what would be a highly-provocative, medium-range missile launch, Park has in recent days made some conciliatory gestures to the regime in Pyongyang.
In a meeting with her ruling party officials on Friday, Park said that the South should meet with the North and "listen to what North Korea thinks".
While Kerry berated Pyongyang's "unacceptable" rhetoric and warned that any missile launch would be a "huge mistake," he also took pains to stress US backing for Park's initiative.
"President Park was elected with a different vision for the possibilities of peace and we honour that vision ... and we hope that vision is the one that will actually take hold here," he said.
"We're prepared to work with conviction that relations between North and South can improve and they can improve very quickly," he added.
In a joint statement released just before Kerry left for Beijing, the United States said it welcomed the "trust building process" proposed by Park.
But Kerry also made it clear that reducing tensions would require cooperation from all sides, and in particular China, whose trade and aid have propped up its ally North Korea since the end of the Cold War.
"China has an enormous ability to help make a difference here, and I hope that in our conversations when I get there that we'll be able to lay out a path ahead that can defuse this tension," he said.
Kerry will hold talks with Chinese Foreign Minister Wang Yi on Saturday and meet the country's new president, Xi Jinping.
Without naming any countries, Xi said last weekend that "no one should be allowed to throw a region and even the whole world into chaos for selfish gains".
French Foreign Minister Laurent Fabius said Friday China's leaders were "very concerned" about the crisis and were working to reduce tensions.
"The Chinese have told us that they are doing their utmost to ease the tension," he said in Beijing after meeting Xi.
After China, Kerry heads to Japan which is also deeply involved in the North Korea issue and which deployed Patriot missiles around Tokyo this week ahead of the North's expected missile launch.
Kerry said he hoped China, Japan and the United States would be able to find the "unity" required to offer a "very different set of alternatives for how we can proceed and ultimately how we can defuse this situation".
Although China holds far more leverage over North Korea than any other country, it has been frustrated by Pyongyang's persistent defiance of its warnings and admonitions.
Observers say China could push harder but is wary of destabilising North Korea for fear it might collapse and be replaced by a reunified Korea allied with the United States.