Yet Beijing seems prepared to absorb the cost to its reputation, confident that in terms of territory and resources, it won't lose a thing.
Despite pressure from Washington and elsewhere, China appears determined to avoid granting any hint of legitimacy to a process that might challenge its claim to ownership of virtually the entire South China Sea, including its islands, reefs, fish stocks and potentially rich reserves of oil and gas.
The collateral cost, analysts say: harm to global efforts to resolve similar territorial disputes through legal means. By its actions, China is demonstrating that countries can reject such measures whenever they conflict with their interests.
A decision is expected sometime within the next several weeks, but since there is no enforcement mechanism, its potential impact is unclear.
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Along with China and the Philippines, four other governments Brunei, Malaysia, Taiwan and Vietnam also claim islands and reefs falling within the nine-dash line, while Indonesia has expressed concern about the Chinese boundary overlapping with its exclusive economic zone.
For months, Chinese officials, state media outlets and high-ranking military officers have maintained a relentless stream of invective against the Philippines' pursuit of arbitration, calling it unlawful, illegitimate and a "political farce."
That the panel is headed by a former diplomat from China's old nemesis, Japan, makes it even more worthy of derision, Chinese critics say.
"The ruling can't be objective and fair, and we won't be giving up our historical rights simply to make China look good," said Wu Shicun, president of the National Institute for South China Sea Studies.