Is Japan’s increasing security assistance with the Association of Southeast Asian (ASEAN) member states through its ‘Official Security Assistance” (OSA) aimed to challenge the heavy presence of China in the South China Sea?

In recent years Tokyo has been building up its military capabilities in response to what it considers to be an increasingly dire security climate in East Asia. For the first time in postwar history, Japan’s defence spending reached its highest level in 2025. The increase in defence expenditure is indicative of Japan’s ongoing progress to achieve its updated security goal of directing 2% of GDP towards defence expenditures by 2027, however it is now anticipated to be accomplished sooner under Prime Minister Sanae Takaichi’s leadership

During the 28^th ASEAN-Japan summit in Kuala Lumpur 2025, Prime Minister Takaichi expressed a desire to strengthen Japan’s security cooperation with the Southeast Asia region, noting the planned expansion of the OSA to more ASEAN states. Since the OSA was launched in 2023, three of the ASEAN member states, Indonesia, the Philippines and Malaysia became recipients of the scheme, with Thailand set to join soon. These ASEAN countries except Thailand are direct claimant states against China’s nine-dash line used to claim 90% of the South China Sea. In the near future Japan is keen to expand the OSA’s reach to more countries, with Cambodia, Vietnam and Laos identified as priority candidates

The OSA is a cooperation framework formed under Japan’s Free and Open Indo-Pacific (FOIP) initiative. The main objective of the FOIP is to promote peace, stability and prosperity across the Indo-Pacific region by ensuring the rule of law, freedom of navigation and overflight, peaceful settlement of disputes, and promotion of free trade.

According to Japan’s ministry of foreign affairs, the OSA scheme seeks to “strengthen Japan’s defense capabilities under the FOIP, as well as to enhance the security and deterrence capabilities of like-minded countries to prevent unilateral attempts to change the status quo by force, to ensure peace and stability of the Indo-Pacific region and create a security environment desirable to Japan. The OSA program supplies partner nations with non-lethal defence equipment, patrol boats, communication systems, marine domain awareness equipment, and coastal surveillance radars. The current OSA guidelines does not allow the supply of offensive weapons meant for direct combat use.

While the existence of the OSA is not only focused on increasing security capabilities with ASEAN member states, one cannot overlook Japan’s interest to expand the scheme in the Southeast Asia region. It can be considered to be a counter measures to China’s continued assertiveness in the disputed waters of the South China Sea, despite the 2016 arbitration ruling under the United Nations Convention of the Law of the Sea (UNCLOS)  in a  case brought by the Philippines against China. The International Tribunal for the Law of the Sea ruled in favour of the Philippines, confirming the rights of the Philippines to control its territorial waters and maritime features, as recognized by UNCLOS. However, China rejected the ruling, citing it to be illegal, null and void. Beijing’s position has always been to resolve the regional maritime disputes of the South China Sea through engagements with direct claimant states.

However, it is worth noting that Japan’s acts to counter-balance the rise of China in the South China Sea have thus far been non-confrontational and focused on several tools such as Coast Guard cooperation, and military exercises. Recently the foreign ministers of Japan and the Philippines convened to strengthen their pledged commitment to the international rules-based order in the South China Sea dispute. Tokyo and Manila have significantly deepened military ties in recent years, joining a security partnership with Washington, and Japan supplying patrol boats and radio gear to the Philippines. The expansion and the sharp budget increase of the OSA signify Japan’s intentions to continue to play a pivotal role in the Indo-Pacific maritime issues in which Japan is seen as a supportive and reliable partner in times of global turbulence

Mr. Kenny Selauli has a Masters degree in Diplomatic Studies from University of Pretoria, an honours degree in political and international studies from Rhodes University. He is currently a research officer at the Institute for Global Dialogue. His views do not necessarily reflect those of the IGD