China has dangerously increased tensions in the South China Sea by deploying an oil rig for the first time in a disputed area claimed by Vietnam. The move is certain to make countries in the region feel even more threatened by China's expansionist territorial claims. The rig, belonging to a state-owned oil company, was parked in waters off the Paracel Islands on May 2. After Vietnam objected, China dispatched 80 ships to the area; Hanoi responded by sending 35 ships to obstruct the rig's operations. The situation escalated on Wednesday, when Vietnam accused China of ramming and using water cannons on several Vietnamese ships. On Thursday, a Chinese Foreign Ministry official accused the Vietnamese of ramming Chinese vessels 171 times in a four-day period and argued that China's use of water cannons showed maximum restraint and was justified because the drilling was in “China's inherent territory.” On Friday, Beijing accused America of encouraging Vietnam's behavior.

China's protestations are not convincing, because there would be no face-off if it had not deployed the rig. Vietnam says the structure is parked on a continental shelf where the United Nations Convention on the Law of the Sea guarantees Vietnam exclusive rights to hydrocarbon and mineral resources. China, which rejects this argument, has laid claim to most of the South China Sea, a vital world trade route. As a result, China is also in conflict with the Philippines, Brunei, Malaysia and Taiwan, which have rival interests in the sea, its islands and its rocks. Some experts say the Chinese deployed the rig because oil and gas reserves were recently found nearby. But the move could also be pushback against President Obama and his increased focus on Asia. On a recent trip to Asia, Mr. Obama said America would defend disputed islands in the East China Sea under its security treaty with Japan and reinforced a treaty commitment to the Philippines. Washington takes no side in the maritime disputes but insists that they must be resolved peacefully.

On Thursday, China offered to hold talks with Vietnam, but only after the ships are withdrawn. In March, the Philippines, which has had frequent face-offs with China over disputed islands in the South China Sea, brought a case against China over a tiny reef to the international arbitration tribunal in The Hague under the law of the sea convention. Vietnam should pursue a similar remedy. Although a signatory to the convention, China has opted out of international jurisdiction over some territorial issues. If China really believes it has a right to drill near Vietnam, it should not be afraid to defend the claim within this internationally authorized dispute mechanism. Given China's increasingly aggressive behavior, Vietnam and its neighbors need a unified response. A summit meeting of Southeast Asian nations in Myanmar this weekend offers a chance to formulate that response. It should include support for using the Hague tribunal to adjudicate maritime claims, while holding out the prospect of joint oil and gas development projects with China. (The New York Times)