The Obama administration can’t seem to resist the temptation to meddle in the territorial disputes between China and its neighbors over islands (and probable underlying oil and gas riches) in the South China Sea. The latest incident began earlier this year when the Philippines filed an unprecedented arbitration case—over Beijing’s strenuous objections—regarding the issue with the United Nations’ Convention on the Law of the Sea. Instead of remaining quiet on the matter, as prudence would dictate, Secretary of State John Kerry ostentatiously weighed in at the East Asia Summit on October 10 in Brunei.

In remarks to leaders at the gathering, including Chinese Premier Li Keqiang, Kerry tacitly backed Manila’s arbitration ploy and its underlying territorial claim. “All claimants have a responsibility to clarify and align their claims with international law. They can engage in arbitration and other means of peaceful negotiations.” In a passage implicitly rebuking Beijing’s extraordinarily broad assertions of sovereign rights in the South China Sea, Kerry added that “freedom of navigation and overflight is a linchpin of security in the Pacific.”

This was hardly the first time that Washington has taken a stance that seemingly embodies an “anyone but China” attitude regarding the South China Sea controversy. During President Obama’s first term, Secretary of Defense Leon Panetta made remarks during a high-profile visit to Vietnam that appeared sympathetic to that country’s claims as well as a bid for bilateral strategic cooperation.

But it is the Obama administration’s support for Manila and its claims that is the most provocative. During a November 2011 East Asian economic summit in Bali, President Obama went out of his way to emphasize the importance of the long-standing U.S. military alliance with the Philippines and pledged to strengthen those ties. Just a day earlier, Secretary of State Hillary Clinton struck the same theme during remarks in Manila, asserting that “the United States will always be in the corner of the Philippines and we will stand and fight with you.” That comment was combative enough in the abstract, but it became even more so when she juxtaposed it with comments about the South China Sea dispute elsewhere in her speech. “Any nation with a claim has the right to assert it,” Clinton stated, “but they do not have the right to pursue it through intimidation or coercion.”

Chinese leaders no longer try to conceal their annoyance regarding Washington’s apparent bias against Beijing’s position. When asked about Kerry’s remarks, Foreign Ministry spokesperson Hua Chunying contended that “non-parties to the dispute should respect the efforts by relevant parties involved to peacefully solve the dispute” through direct negotiations, “instead of doing things that could harm regional peace and stability.” She added (with considerable exaggeration) that “the South China has been calm and tranquil, so if some country really wants to safeguard peace and stability in the South China Sea, it should stop stirring up waves.”

Beijing’s claims are annoyingly broad, and the United States, as the world’s leading maritime power, understandably does not want to see the South China Sea become Chinese territorial waters. But Washington needs to exercise greater caution for two reasons. First, the issue is one that involves a great deal of national pride on China’s part, not just mundane economic or territorial calculations. Chinese officials are fond of asserting their country’s “indisputable historical” claim to the South China Sea and seem to regard U.S. actions as a manifestation of a broader policy to thwart China’s re-emergence as a great power. Chinese leaders are already uneasy about Washington’s strategic pivot or “rebalancing” military posture toward East Asia and the accompanying efforts to strengthen ties with traditional allies such as Japan and South Korea. Backing the Philippines and other rival claimants in the South China Sea controversy enhances Beijing’s suspicions.

Second, it is generally a bad idea for a great power to back a small, volatile client state in a dispute with a much larger, stronger neighbor. Small clients then have a tendency to adopt a bolder stance—sometimes even an irresponsible one—confident that their powerful patron has their back. Serbia’s actions in 1914 toward Austria-Hungary might have been far less intractable if Belgrade had not assumed that it had Russia’s support. And more recently, the Georgian government’s provocative military actions against the Russian-protected secessionist regime in South Ossetia seemed motivated in part by the mistaken belief that the United States and NATO would protect the country from Moscow’s retaliation.

The Philippines is a small, poor country with a fragile political system marked by a good deal of jingoistic posturing.Its territorial claims in the South China Sea may exceed any reasonable ability to vindicate them without direct U.S. backing. Manila has already infuriated Beijing on several occasions over the past few years by sending ships into disputed waters. Washington’s imprudent support for a weak treaty ally could ultimately embroil the United States in a nasty confrontation with an increasingly powerful China. The Obama administration needs to rethink its strategy regarding the South China Sea issue before blundering into a crisis.