TOKYO - US Vice-President Joe Biden arrived in Tokyo late on Monday for the first leg of a tour of East Asia that will later take him to China and South Korea.
Biden's visit comes amid mounting tensions between China and Japan over territorial claims and China's announcement last month of its East China Sea Air Defence Identification Zone.
Biden is walking a diplomatic tightrope, according to observers, with various parties calling on him to support their stances, while others look to the US to calm tensions.
Japanese Prime Minister Shinzo Abe said on Sunday that he would discuss China's air defence identification zone with Biden on Tuesday to coordinate their stances.
"We want to hold consultation and deal with the matter by coordinating closely between Japan and the United States," Abe said.
One day before Biden's arrival, the US Navy's first advanced P-8 patrol aircraft arrived in Japan, starting a deployment that will upgrade Washington's ability to hunt submarines and other vessels in seas close to China, Reuters reported.
White House officials have emphasised that the visit is part of a continuum of US engagement in the Asia-Pacific region.
"The trip will underscore the Obama administration's strong commitment to the rebalance and to our enduring role as a Pacific power," a senior administration official said last week.
"It is an opportunity to give lift to our treaty alliances and to advance our very important relationship with China," the official said of Biden's trip.
Observers said that pacifying Tokyo and communicating with Beijing might be Biden's main task, but it will be difficult for him to achieve an arrangement that is satisfactory for all parties.
Stapleton Roy, a scholar at the Kissinger Institute on China and the United States at the Wilson Center, said that the US and China share a major responsibility to act wisely and responsibly in dealing with regional sources of tension.
"Neither of the two countries should let the passions of the moment drive their behaviours," said Roy, who was also the US ambassador to China in the early 1990s.
However, Zha Daojiong, a professor of international relations at Peking University, said Washington appears to be increasingly taking a leadership role in the diplomatic impasses among Tokyo, Beijing and Seoul - a role that many in Washington would rather not take on.
"The truth of the matter is that the expectations of the three northeast Asian capitals for 'reassuring' words and actions from Washington DC could easily put the US desire to satisfy everyone under strain," Zha said.
"As such, realistically, the Biden trip can and should function as one that personifies the usual US call for restraint on the part of each of the three Northeast Asian capitals, rejecting conflict, which no party desires," he added.
Since China announced its air defence identification zone on Nov 23, Washington has repeatedly voiced its rejection of the zone, even flying two B-52 bombers to show defiance, although the Pentagon said the flights were part of long-planned military drills.
Tokyo and Seoul also refused to recognise the zone, which overlaps with Japan's ADIZ over China's Diaoyu Islands in the area, and both have flown planes over China's zone without reporting to the Chinese authorities ahead of time. In return, China said it has dispatched air force jets to monitor these aircraft.
Wu Xinbo, director of the Institute of American Studies at Fudan University in Shanghai, said that Beijing's air defence identification zone covers an area that features the most frequent US military activities in the region, and thus has infringed on the so-called "US strategic interest".
"It definitely impacts the low-altitude US reconnaissance against China and its joint exercises with allies. The bombers were dispatched to the zone only as a demonstration of Washington's tough posture," Wu said.
China has also asked aircraft to submit flight plans when traversing the area.
In defiance, Tokyo has ordered Japanese airlines not to submit flight plans to Beijing, but Washington said on Friday that it generally expected US carriers to "operate consistent with" notification policies issued by foreign countries.
Foreign Ministry Spokesman Hong Lei expressed on Monday his appreciation for the constructive attitude of several airlines that have reported flight information to Chinese authority. He also urged Japan to stop making groundless accusations and take joint responsibility with China in safeguarding aviation control in the airspace.
"The fact that Tokyo has deliberately politicized the matter is not conducive to bilateral cooperation in civil aviation," Hong said.
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Pu Zhendong in Beijing and Reuters contributed to this story.