This commentary originally appeared in Nikkei Asia.

The Association of Southeast Asian Nations is due to hold its first joint naval exercise as a bloc next month.

This will be an important milestone at a time the group is facing daunting challenges to its interests and its diplomatic centrality in the Asia-Pacific region, including intensifying U.S.-China rivalry; an ongoing crisis in Myanmar that has divided ASEAN and left it looking feeble; the proliferation of alternative forums including AUKUS and the Quad; talk of a NATO office in Japan; and, of course, China's continued assertiveness in the South China Sea.

The upcoming drill, though, could have been a bolder, more assertive statement.

Indonesia, as ASEAN chair, initially proposed holding the exercise within the South China Sea. Unfortunately, due to Cambodian opposition, the exercise has been shifted to an area outside of China's expansive South China Sea claim. The Cambodians are said to have argued that the initial location of the drill, in the North Natuna Sea, would have unnecessarily upset China.

The decision to shift the exercise is a minor blow to ASEAN ambitions to bolster security cooperation but should not deter Indonesia and other member nations from making another run at a collective Southeast Asian naval drill in waters that fall within China's infamous "nine-dash line."

Such a drill would not only make sense from a policy and international law perspective but arguably reinforce one of the original intentions behind the founding of ASEAN in 1967, and address its current need to reaffirm the bloc's centrality.

ASEAN was established as a bulwark against communist expansionism and also to manage conflict and mistrust among neighboring Southeast Asian nations. The intention was to discourage great-power intervention and interference in the region.

The past 10 to 15 years, however, have seen significant intervention in the South China Sea, most notably by China, which continues to assert its expansive claim vigorously despite a ruling by a U.N.-backed tribunal that its nine-dash line claim has no basis in international law.

China's aggressiveness has prompted the U.S. and others to increase naval activity in the region to assert the right of navigation through what they maintain is an international waterway. Many ASEAN nations have complained about or felt uncomfortable with these activities, particularly those of China, but the bloc has struggled to back up its position with tangible action.

That is the beauty of an ASEAN naval exercise in the South China Sea. Properly designed and implemented, it would assert ASEAN centrality on a critical issue and put China on the back foot, without bringing in great power competition.

China would probably protest, but it is hard to imagine Beijing retaliating against a substantial group of Southeast Asian nations -- countries it is actively wooing -- acting together. The U.S. probably would welcome ASEAN's action, which would advance the cause of treating the area as international waters without its own involvement.

To be successful, the exercise would need to include only ASEAN members, as any outside participation would undermine the whole point. As Indonesia originally proposed, it should also be run as a humanitarian relief exercise rather than anything more overtly "military."

Such an exercise would not resolve South China Sea territorial claims nor prevent China from continuing to assert its claims. Nor would it end the bloc's divisions over Myanmar or other matters. It would, however, boost ASEAN's diminished credibility, while pushing back on unjustified Chinese claims in a manner that Beijing would not easily be able to counter or blame on the U.S.

If the initial exercise were carried off successfully, it could lead to regular drills, potentially reducing the perceived need in Washington and other capitals to assert freedom of navigation rights in the South China Sea themselves. In that sense, it could reduce great-power tension and "interference" in the region.

The big question, of course, is how Indonesia and other proponents can overcome the objections of Cambodia, and possibly other member states.

Perhaps further discussions within the bloc could produce a plan that all members could accept. In the more likely case that divisions persist, then Indonesia, as ASEAN chair, could organize a naval exercise open to any bloc member willing to participate.

This presumably would include Singapore, Malaysia, the Philippines, Vietnam and ideally Thailand, at least.

Such a "minilateral" approach would be unusual but feasible, particularly if no external powers are involved. After all, Thailand recently broke with established ASEAN consensus to host a minilateral meeting on Myanmar that upset some of its fellow member states.

If need be, countries participating in a South China Sea drill could call it an "informal" ASEAN exercise to get around the lack of consensus. If the six mentioned countries all participated, it would still send a strong signal that ASEAN can, formally or informally, still act on critical issues.

ASEAN has a chance to take a significant step that would be in line with its original purpose and that would do much to bolster its standing, and possibly even reduce great power tension in the South China Sea. Indonesia and other like-minded ASEAN members should seize the chance and make it happen, especially since Indonesia is due to pass on the role of bloc chair to Laos, whose government is particularly susceptible to Chinese influence, later this year.