America's top diplomat will press China and South Korea not to let regional disputes escalate into armed conflict during an Asian tour that started yesterday.
US Secretary of State John Kerry, who will pave the way for a visit to the region by President Barack Obama in April, arrived in Seoul on his way to Beijing where he will tell officials that the US is committed to a positive relationship with China, the State Department said.
"It is unwise in the extreme for China to take actions that are disruptive of stability in the region," a senior State Department official told reporters travelling with Kerry on the plane to Seoul.
The six-day trip, which also includes Indonesia and Abu Dhabi, comes amid heightened tensions in the Asia-Pacific region, led by China and Japan's territorial dispute in the East China Sea.
Kerry's latest tour of Asia, his fifth in the past year, highlights increasing US concerns about being dragged into conflicts between Beijing, Seoul and Tokyo, plus worries over North Korea's nuclear programme.
Kerry is not visiting Japan, but he met Japanese foreign minister Fumio Kishida last Friday in Washington, where the two pledged to collaborate further on security and oppose China's declaration of an air defence identification zone. Kerry is expected to relay US opposition to that move while in Beijing .
"The US will press China to take a more cautious approach to maintain stability in the East China Sea," said Jia Qingguo, an international relations professor at Peking University. "The US is obviously very worried that it will be involved if there is armed conflict between China and Japan."
Shi Yinhong, a US affairs expert at Renmin University, said Kerry would probably demand that China does not declare an air defence zone in the South China Sea, but China was unlikely make such a promise.
The US official, who did not want to be named, said the US would urge the maritime and island claimants in the South and East China seas to clarify their claims in line with international law, including the UN Convention on the Law of the Seas.
Washington's worries about the region were heightened in December when Japanese Prime Minister Shinzo Abe visited the Yasukuni Shrine in Tokyo, and even criticised its Japanese ally for stoking tensions.
While the incident deepened China's mistrust of Japan and the US, it also exacerbated Tokyo's suspicions that Washington may abandon it, said Sun Zhe, an international relations professor at Tsinghua University.
"The US is trying to strike a balance in the region, which is a very tricky task," Sun said.
Watch: Kerry tells N. Korea to get 'real'
Tokyo and Seoul are also vying for attention from Washington as they confront each other over territorial disputes and their wartime past.
Also topping the agenda during Kerry's visit will be North Korea's nuclear programme. Kerry will discuss co-ordinating policies towards Pyongyang with Seoul and Beijing.
Pyongyang has said it is willing to return to the stalled six-nation nuclear talks, but South Korean Defence Minister Kim Kwan-jin said this week preparations for a test at North Korea's main underground nuclear site appear to be complete.
Additional reporting by Agence France-Presse