TOKYO (THE YOMIURI SHIMBUN/ASIA NEWS NETWORK) - Tensions are escalating as China is accelerating its use of the South China Sea as a military hub.

A "change made in the status quo by force" should not be allowed to become a fait accompli, and the countries concerned must unite to stop it and maintain regional stability.

Chinese troops conducted military exercises near the Paracel Islands in the South China Sea, over which China and Vietnam have a territorial dispute. There is speculation that China may soon conduct a large-scale exercise there involving aircraft carriers.

China has also suggested the possibility of setting up an air defence identification zone in the South China Sea.

This reflects Beijing's claim that its sovereignty covers almost the entire area of the South China Sea. That claim was dismissed in 2016 by the court of arbitration's ruling.

It is extremely irresponsible of China to ignore the ruling.

At the summit meeting of the Association of Southeast Asian Nations (Asean), Vietnam, Indonesia and other member countries voiced concern over China's behaviour, which does not respect the rule of law.

The chairman's statement confirmed the importance of freedom of navigation and also freedom of overflight.

The problem is that China has been intensifying its activities in the South China Sea amid the delay in formulating a code of conduct to prevent conflicts between China and Asean.

Discussions on formulating the code have been suspended due to the novel coronavirus pandemic, and it is uncertain whether the code will be realised in 2021 as targeted.

China has stressed that the code of conduct - developed by countries involved - would lead to stabilising regional conditions. There is no doubt that Beijing's assertion is aimed at excluding the involvement of Japan, the United States and other countries.

China's military expansion has had a major impact on the entire Asia-Pacific region, including Japan. Countries in the region, such as Japan, the United States and Australia, need to support Asean from the standpoint of respecting international rules and protecting freedom of navigation.

It is hoped that cooperation will be strengthened among the countries involved, using opportunities such as a multinational naval exercise as part of the Rim of the Pacific (RIMPAC) Exercise administered by the US Navy, which will be conducted in waters near Hawaii in August.

The US military recently conducted an exercise with two aircraft carriers in the South China Sea to coincide with Chinese military drills. It is unusual for the United States and China to conduct military exercises at the same time.

There are persistent concerns among Asean member countries that the administration of US President Donald Trump is weakening its involvement in Asia.

It is important that the United States will continue to work to keep China in check in the South China Sea, while taking care not to increase military tensions.

Chinese government ships that entered Japan's territorial waters off the Senkaku Islands recently committed a record-long intrusion of 39 hours.

A recent law revision in China allows Chinese government ships to conduct operations under the military command during wartime.

There are fears that Beijing's provocations around the Senkakus could take on a more military tone. Japan should be more vigilant.

The Yomiuri Shimbun is a member of The Straits Times media partner Asia News Network, an alliance of 24 news media organisations.