While Southeast Asian nations have repeatedly warned against being forced to choose between China and the US, the past few days have only confirmed that the strategic rivalry now reaches deep into the political heart of the region.
The historic failure of Asean foreign ministers to agree on the wording of a routine communique mentioning the South China Sea is one symbol; increased Sino-US commercial competition over Myanmar and Cambodia - for decades a blood-soaked proxy battlefield for superpowers - is another.
The failure over the communique is particularly dramatic. And it is producing fears that it could yet poison upcoming talks with China over a long-awaited code of conduct to govern disputes in the South China Sea.
It produced open tensions yesterday as the top envoys of Cambodia, the meeting host, and the Philippines took pot-shots at each other - a highly rare event given the Association of South East Asian Nations faith in consensus, and tradition of keeping fights 'within the family'.
Cambodian Foreign Minister Hor Namhong said he regretted the discord, but he 'could not accept that the communique had become hostage of the bilateral issue (between the Philippines and China)' - echoing earlier language from Beijing.
For several days ministers had argued in private over a Philippines demand to include a reference to its standoff with China over the Scarborough Shoal, known in Chinese as Huangyan.