China's latest white paper mentions "offshore waters defence and open seas protection", explicitly declaring Beijing's hardened determination to actively defend its territorial ambitions in adjacent waters, while Washington has stepped up its surveillance operations close to Chinese reclamation activities.
With little sign of compromise on the horizon, the Philippines and Japan, two of America's closest allies, have stepped up their strategic partnership against China.
Recently, Philippine President Benigno Aquino embarked on a four-day state visit to Japan, where he negotiated the parameters of expanded Philippine-Japan maritime security co-operation, potentially paving the way for Japanese access to military bases in South-east Asia. The trip was of great strategic significance to both countries.
Since 2011, as Sino-Japanese territorial tensions in the East China Sea picked up, Tokyo has reached out to like-minded countries in the region, striking strategic partnership agreements with the Philippines as well as Vietnam, which are also locked in a bitter maritime dispute with Beijing.
In recent years, Japan, which is the Philippines' biggest source of Overseas Development Assistance (ODA), has supported the South-east Asian country's efforts to develop a minimum deterrence capability in the light of rising tensions in the South China Sea.
Together with the United States, Japan has also called for a robust information-sharing system in South-east Asia in order to enhance coordination and surveillance amid China's expanding presence in the area.
Calling for "pro-active pacifism", and eager to ease decades- long restrictions on Japan's ability to project power beyond its immediate shores, Prime Minister Shinzo Abe is trying to carve out a new security role for Japan by pushing back against Chinese maritime assertiveness in the South China Sea.
Mr Abe has reiterated that Japan, along with its South-east Asian partners, particularly the Philippines, shares "serious concern about large-scale land reclamation and that we oppose any attempt to unilaterally change the status quo".
But in order for Tokyo to play a more consequential role in the region, it has to overcome lingering anxieties, at home and among neighbours, over the alleged erosion of Japan's pacifism as well as strike security agreements that allow for the resupply and refuelling of Japanese Self Defence Forces beyond Japan's immediate waters.
Mr Aquino's state visit to Tokyo represented a crucial opportunity for the Abe administration to show how neighbouring countries like the Philippines, which was among the biggest victims of Japanese imperial aggression during World War II, are supportive of Japan's bid for a greater role in the region.
This year is particularly sensitive, since it marks the 70th anniversary of the defeat of Axis powers during World War II, and Japan's neighbours, particularly China and South Korea, are expected to raise concerns over the alleged remilitarisation of Japan under the nationalist government of Prime Minister Abe.
The Filipino President, who delivered a speech before the joint session of the Japanese Parliament (Diet) earlier this month, emphasised the common destiny of the two countries and how they confront the same threat in the region. He said: "The prosperity of maritime and coastal East and South-east Asia, which relies greatly on the free movement of goods and peoples, is at risk of being disrupted" by China's maritime assertiveness in the Western Pacific.
Mr Aquino and Mr Abe also discussed more tangible areas of co-operation such as the possible export of P-3C anti-submarine reconnaissance aircraft and radar technology to the Philippines and the delivery of 10 advanced patrol vessels worth $150 million to the Philippine Coast Guard.
Crucially, the Philippines and Japan started negotiating a bilateral Visiting Force Agreement, which could potentially grant Japan rotational access to Filipino bases. This will allow the Japanese Maritime Self Defence Forces to refuel and resupply if and when Tokyo pushes ahead with plans to conduct joint aerial patrols with the US in the South China Sea.
But with Mr Aquino entering his final months in office, it is unclear whether he wields enough political capital and time to gain the support of the Philippine Senate to ratify any major military agreement with Japan.
Most likely, the task will fall on the succeeding administration, which may similarly welcome closer security ties with Japan. Still, the Philippine-US Enhanced Defence Cooperation Agreement, signed in the middle of last year, ahead of President Barack Obama's visit to Manila, has yet to be cleared by the Philippine Supreme Court. So legal hurdles abound.
Nonetheless, the Philippines is desperate to gain as much external support as possible, especially in the light of fears that China may soon have the ability, thanks to its sprawling facilities and expanding patrols in the contested areas, to choke off the supply lines of other claimant countries in the Spratly chain of islands and push ahead with imposing an Air Defence Identification Zone in the South China Sea.
Both Tokyo and Washington consider freedom of navigation in the area as a national interest issue. Japan's energy-hungry and trade-dependent economy could be adversely affected by any conflict in international waters such as the South China Sea. As one Japanese defence official put it, in an interview with Reuters, "we have to show China that it doesn't own the (South China) sea".
Key American allies such as Australia have reiterated their determination to continue maritime patrols in the South China Sea, and Washington is eager to see Japan chipping in.
Under the notion of "collective security", and in accordance with the revised US-Japan bilateral defence guidelines, Tokyo is expected to widen its area of operation in assisting its allies and contributing to international security.
Overall, it is clear that China's rising maritime assertiveness has facilitated a greater strategic footprint for Japan in South-east Asia, especially as smaller claimant countries such as the Philippines actively seek greater international military and diplomatic assistance in the South China Sea.
This article was first published on June 18, 2015.
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