A row about disputed islands between China and Japan has raised tensions in East Asia. In the latest development, China has demarcated an air defence identification zone which includes the islands, called Senkaku in Japan and Diaoyu in China, prompting protests from Japan and the US. Five experts give their views.
Overview: James Manicom, Centre for International Governance Innovation, Canada
The dispute over the Senkaku/Diaoyu islands is more than 30 years old and tensions over the East China Sea have flared periodically since 2000 as China has become a more proactive maritime power. However, since the nationalisation of the islands by the Japanese government in September 2012, the dispute has taken on a decidedly more ominous character.
Both governments are motivated to maintain their claim to the islands through acts that reinforce their sovereignty and neither government has the incentive to back down.
Japanese leaders deny the very existence of a dispute over the islands and Shinzo Abe's foreign policy platform, which rests on the notion of Japanese resurgence, reflects a broader reluctance in Japan to tolerate further perceived Chinese encroachments into Japanese territory.
Chinese leaders seem determined to undermine the Japanese claim over the islands by challenging Japan's administration of the islands and the waters that surround them. To this end it has regularised patrols of the territorial sea by its coast guard, announced base points around the islands and, most recently, included the islands in its air defence identification zone (ADIZ) that encompasses much of the East China Sea.
The question remains whether China will try to occupy the territory of the Senkaku/Diaoyu islands in some way, which could potentially trigger armed conflict between China and Japan and potentially the United States.
Despite the escalation of tensions however, there has been considerable informal discussion about ways to improve ties. There have been a number of meetings between various ministries on confidence and transparency building between naval and coast guard forces in the East China Sea. Furthermore, in early 2013 both leaders publicly articulated a willingness to rebuild ties with the other.
The two sides have a decent track record of dispute management characterised by ignoring the sovereignty dispute over the islands and by managing the jurisdictional disputes that arise in the surrounding waters over fisheries or resource development.
Two key uncertainties are the conditions under which the two will begin improving their relationship and the stability of any new "status quo" that will be negotiated around the islands.
China's ADIZ announcement suggests that Chinese leaders are only interested in talks with Japan under conditions including parity in authority exercised over the surrounding seas and an admission by Japan that a dispute exists over the islands.
Neither of these conditions is acceptable to Tokyo, which has offered to concede that the two have a territorial "problem" rather than a dispute. However, despite their de facto acceptance of periodic Chinese patrols of the territorial sea since the nationalisation, it is not clear that Japan will accept in perpetuity daily intrusions into these waters by Chinese ships and aircraft.
On balance the prognosis is negative. Despite the stated willingness to co-operate, it is not clear the two sides agree on the conditions that would form the pretext of closer ties.
Continued Japanese restraint in the face of Chinese efforts to modify the status quo is currently keeping the peace, potentially to the detriment of Japan's claim to the islands and its ability to use the surrounding sea area. It is not clear that the Abe administration will tolerate this situation indefinitely.
China: Victor Gao, Director of the China National Association of International Studies
Japan seems to ignore the fact that it has demarcated a similar identification zone in the East China Sea for years, and has expanded this zone over the years. In fact, the western-most line of Japan's zone stretches all the way to China and is only about 135km (84 miles) from China's coast at the closest point.
In recent years, Japan has on many occasions scrambled fighter planes to warn off Chinese planes when they entered the Japanese zone, as if the zone were Japan's territorial space. In a sense, China's announcement of an identification zone is in response to Japan's abusive use of its zone to start with.
It is important to note that the Chinese and Japanese zones overlap to a large extent. Therefore, both nations need to handle themselves carefully and prudently to avoid any miscalculations or unintended consequences.
However, the fundamental reason for the deterioration of relations between Japan and its two important neighbours, China and South Korea, is because Japanese Prime Minister Shinzo Abe and many Japanese politicians still refuse to acknowledge war atrocities.
They deny the existence of the Nanjing Massacre, they claim the Korean sex slaves worked voluntarily, they continue to worship at the Yasukuni Shrine. They also want to abandon the peace commitment set out in the Japanese constitution, and rearm.
Although Japan is doing its utmost to tie the United States to its bandwagon, China and the US are significantly increasing their military co-operation and strategic dialogue.
After all, China and the US shed blood together to defeat Japan in WWII, and, with increasing dialogue and confidence-building measures between Beijing and Washington, it is highly unlikely that the US will shed blood to encourage or even to protect a militarising Japan.
China is urging Japan to unequivocally renounce the war atrocities and come back to the negotiating table regarding the territorial dispute over the Diaoyu Islands.
China and Japan can only resolve this dispute through peaceful negotiations. Recognising the territorial dispute and coming back to the negotiating table is the only sensible choice for Japan.
Japan: Tetsuo Kotani, Japan Institute of International Affairs
The ownership of the Senkaku Islands was reaffirmed under the 1951 San Francisco Peace Treaty, which demarcated Japan's territory after World War II, and the 1971 US-Japan Okinawa Reversion Treaty, which returned the administrative rights of Okinawa, including the Senkaku Islands, from the United States to Japan.
By challenging Japan's control of the islands, China is attempting to introduce a new regional order that favours it. As long as Beijing remains revisionist, it will not be easy to improve relations between Tokyo and Beijing.
Business and cultural exchanges between Japan and China have been recovering since the beginning of this year, but political relations remain difficult. Tokyo is willing to engage in dialogue with Beijing with no conditions. However, Beijing has been pressuring Tokyo to have "negotiations" on the Senkaku Islands, through coercive measures such as putting a fire-control radar lock on Japanese naval forces, and violating Japan's territorial waters and airspace.
Tokyo has tried to reach out to Beijing on various occasions. Prime Minister Shinzo Abe sought a meeting with President Xi Jinping at the G20 and Apec [Asia-Pacific Economic Co-operation] meetings. Tokyo also sent high-ranking officials to Beijing for discussions on crisis management and strengthening communication. Despite the different claims over the Senkaku Islands, Tokyo believes that the two countries need to develop bilateral relations to ensure regional stability and prosperity. Tokyo will continue to seek opportunities to engage with Beijing.
The announcement of China's air defence identification zone (ADIZ) has no legal effect but is an unnecessary provocation. First, it covers the Senkaku Islands, which are under the administration of Japan. Second, it overlaps with Japan's ADIZ. Third, China has announced that all aircraft are obliged to observe Chinese regulations. These measures are totally against international practices. The announcement will simply increase existing tensions in the East China Sea and the chance of clashes.
If China implements its ADIZ, it is likely that there will be frequent encounters between Japanese and Chinese fighters in the overlapping zones. It is also likely that Washington will implement the freedom of navigation programme, its policy of asserting its navigational rights, by sending aircraft into China's ADIZ to challenge China's excessive claims. The worst-case-scenario is a collision that could escalate into a larger conflict if managed badly.
In order to ease tensions, Beijing should stop its provocative and coercive measures. These measures will not bring any compromise from Tokyo. Instead, Beijing should preserve international laws and norms, and take peaceful measures to resolve the competing claims. Beijing also needs to understand that China can enjoy security and prosperity only under a stable international environment. Beijing should not impede free and fair access to maritime and air spaces.
US: Michael Swaine, Carnegie Endowment for International Peace
Relations have fluctuated somewhat after a very tense period following the Japanese purchase of several of the islands in September 2012.
Various incidents have taken place (for example, a Chinese frigate apparently locking its weapons-targeting radar onto a Japanese destroyer in February 2013, an exchange of sharp words over possible overflights of the islands by Chinese drones in October, various sharp exchanges from officials during the year), but leaders on both sides have also indicated that they would like to reduce tensions, and discussions have occurred at various times over possible ways to open talks aimed at reducing tensions.
Moreover, the number of incidents prompted by Chinese air and sea incursions near the islands has dropped from the highpoint of late 2012. The latest incident (China's announcement of an ADIZ in the East China Sea) has again increased the level of tension, however, making movement toward tension-reducing talks less likely in at least the short-term.
The ADIZ declaration clearly undermines any movement toward a mutual reduction in tension. Despite Chinese protestations to the contrary, the announcement is being viewed by US, Japanese and other observers as provocative and unhelpful.
Since the ADIZ encompasses the Senkaku-Diaoyu Islands, it is feared that it could now be used as a justification for more regular intercepts of Japanese aircraft approaching those islands, thus increasing the likelihood of an incident. Equally troublesome, the ADIZ could also be used to justify more aggressive Chinese responses to foreign military aircraft transiting the zone, even when they are not heading toward Chinese airspace.
Beijing has thus far sent mixed messages regarding how aggressive it might be, for example, in intercepting foreign military aircraft on surveillance missions within the airspace.
Although Beijing has at times in the past sent fighters to intercept such flights along China's coast, sometimes employing aggressive, close-in manoeuvres designed to push back the surveillance aircraft (one such action precipitated the so-called Hainan Incident of 2001 that resulted in the loss of life), the ADIZ might presage a more regular pattern of such interdiction efforts.
It is difficult to say how dangerous the situation is at present. Much depends on how Japan and the US react to the announcement through aircraft deployments. The US has already flown two B52s through the zone east of the islands, without incident.
But a more serious test would come over US or Japanese surveillance flights through the ADIZ, or when Japan sends fighters into the airspace over the islands. Such actions could prompt a greater-than-usual assertive Chinese response than might have occurred before the ADIZ announcement, which could increase the chances of an incident.
And as indicated, much will depend on how the Chinese implement the ADIZ. At the very least, the Chinese need to clarify, authoritatively, how they will treat surveillance aircraft and other potentially "threatening" (from their viewpoint) military aircraft that are transiting the zone but not heading toward Chinese airspace. Thus far, Chinese efforts at clarification have been unsuccessful.
Asean: Lye Liang Fook, East Asian Institute, National University of Singapore
In China's view, Japan altered the status of the islands when it nationalised three of them in September 2012.
Since then, apart from trading verbal barbs, the naval and air assets of both countries have routinely ventured near to or into waters off the islands. A new norm seems to have been set whereby both countries "take turns" to assert their sovereignty over the islands.
Yet China has so far been unsuccessful in getting Japan to admit that the islands are in dispute. Through the announcement of its air defence identification zone (ADIZ), China wants to ratchet up the pressure on Japan.
Japan and the US have reacted most strongly. Japanese Prime Minister Shinzo Abe has described the move as "totally unacceptable for Japan". US Defence Secretary Chuck Hagel called it a "destabilising attempt to alter the status quo".
Japan is also eager to work with South Korea (also directly affected by China's ADIZ) and Australia to mount a concerted response. Relations between China and Japan look set to worsen.
However, developments are not all gloomy. For one, both China and Japan have kept official and unofficial channels of communications between them open. They have also been able to compartmentalise their dispute.
A delegation of senior Japanese business executives called on Chinese Vice Premier Wang Yang in Beijing just days ago. In the midst of the furore over China's ADIZ, working-level officials from Japan, China and South Korea met in Tokyo for their third round of free trade talks. While tensions over the islands are high, exchanges in other areas are continuing.
Neither Asean [Association of Southeast Asian Nations] nor any of its 10 member states has responded to China's ADIZ. This is not surprising as the resolution of the islands issue primarily rests with China and Japan.
However, Asean members do have an interest in regional stability. Their preference seems to be for China and Japan to meet at the negotiating table to sort out any differences rather than for them to constantly test each other at sea or in the air.
Even assuming that Chinese and Japanese top leaders do not wish to see the two sides coming to blows, the probability of a miscalculation or mishap happening at sea or in the air increases with any measure or counter-measure introduced, China's ADIZ included.
There are some who speculate that China could follow up by introducing a similar ADIZ over disputed parts of the South China Sea (SCS). In particular, China could mark a zone that is in dispute with the Philippines in order to force the latter to withdraw its submission against China at the international arbitration tribunal.
If China did so, it is very likely to lose a lot of the credibility that it has painstakingly built up since a fresh set of leaders took the helm this year. More recently, in October 2013, President Xi Jinping and Premier Li Keqiang visited five Asean countries and made numerous proposals to further deepen ties.
China's key message is that the SCS disputes that it has with some Asean claimant states should not stand in the way of the many lucrative opportunities that China and Asean would benefit from.