China sent its first air patrol to back up its newly declared air defense identification zone (ADIZ) over the East China Sea Saturday. Japan scrambled fighter jets in response.

According to China's announcement of the ADIZ, any military aircraft entering it would need to submit their flight plans, maintain radio communication and reply promptly to identification inquiries from Chinese authorities.

China also said that "[its] armed forces will adopt defensive emergency measures to respond to aircraft that do not cooperate in the identification or refuse to follow the instructions." China's ADIZ partially overlaps those of Japan and South Korea, and overlies the disputed Diaoyu islands, known as the Senkaku Islands in Japan.

Japan said that China's new ADIZ potentially escalated the danger of accidental "collisions" between the Chinese military and US, as well as Japanese counterparts, and lodged a "serious protest."

According to US Secretary of State John Kerry, "the US does not support efforts by any state to apply procedures of an air defense identification zone to foreign aircraft not intending to enter its national airspace. We urge China not to implement its threat to take action against aircraft that do not identify themselves or obey orders from Beijing."

On Monday, two US B-52 bombers out of Guam flew into China's new ADIZ without identifying themselves, clearly testing China's reaction. This move seemed to contradict the US position that China and Japan should resolve the issue by diplomatic means.

As usual, there are at least two sides to the issues. From China's perspective, it was simply "leveling the playing field." First of all China has a "right" by precedent and practice to declare an ADIZ to protect its sovereignty over territory and the maritime areas it claims.

Moreover, China's zone does not affect commercial air traffic. Xinhua claimed the ADIZ "could contribute to regional peace and security by curbing the increasing rampancy of Japan's right-wing forces."

Indeed, in China's view, it is an increasingly nationalistic and aggressive Japan that has altered the "status quo" by "nationalizing" the disputed islands. In this context, China's declaration of an ADIZ was probably a reaction to Japan's threat to shoot down China's drones flying over the disputed area.

ADIZs are not new and have always been unilateral and controversial. More than 20 countries have declared ADIZs.

The US has five ADIZs around North America, including a large one off Alaska and the Aleutian Islands, extending several hundred miles out to sea. In this ADIZ, both foreign civilian and military aircraft are monitored and interrogated regardless of destination. The US ADIZ is jointly administered by civilian air traffic control authorities and the North American Aerospace Defense Command.

Any aircraft in this zone without authorization may be treated as a threat, potentially leading to interception by fighter aircraft. The US routinely scrambles jet fighters to intercept Russian bombers in its ADIZ regardless of "destination." In just the last few months, US jets have intercepted Bear bombers in the Alaska ADIZ at least five times.

In theory, overlapping ADIZs are not unusual and can be managed cooperatively as is the case with the US and Canada. But since in the East China Sea they involve airspace over islands and maritime space disputed by two antagonists, they do pose a precarious potential for conflict.

Hopefully all sides will exercise restraint and this situation can be negotiated and resolved with perhaps some voluntary guidelines for conduct of military aircraft in the areas of overlapping ADIZs. Japan and Russia have a regular consultative process "to monitor military interactions and prevent risky behaviors" around the disputed Northern Territories/Southern Kuriles Islands.

But right now there are no formal agreed rules regarding ADIZs or rules and conduct within them. Perhaps a UN-sponsored conference could help formulate an international agreement addressing these issues. Next week's visit by US Vice President Joe Biden to China, Japan and South Korea is an opportunity to initiate a way forward.

The author is Adjunct Senior Research Associate at the National Institute for South China Sea Studies. opinion@globaltimes.com.cn