Pressure on China over its claims to most of the strategic South China Sea went up a couple of notches this week. First the U.S. sent a warship, in its most direct challenge yet to Beijing's artificial island building. Then, over Chinese objections, an international tribunal ruled it had jurisdiction in a case brought by the Philippines on maritime claims.

Neither action appeared likely to stop China in its tracks, as it seeks to assert its control over resource-rich waters that it considers vital to its security. Beijing is expected to put a higher priority on what it sees as its strategic interests than its international reputation.

But it could damage China's efforts to win more respect on the global stage as it emerges as an economic and military power.

The United States, which has had little success to date in its five-year effort to put diplomatic pressure on China over its uncompromising pursuit of claims to more than 80 percent of the South China Sea, is hoping that makes a difference. It welcomed the tribunal decision and said it expected Beijing to abide by the final ruling next year.

Although the tribunal was set up on the basis of a provision of the 1982 U.N. Convention on the Law of the Sea that both the Philippines and China have ratified, China has boycotted the proceedings. On Friday its Foreign Ministry declared that the ruling on jurisdiction was “null and void” and would have no binding effect on China.

The Philippine case, which was filed before the tribunal in The Hague in January 2013, contends that China's massive territorial claims are invalid under the convention. The tribunal on Thursday decided it has jurisdiction in the case.

The tribunal will also examine whether a number of Chinese-occupied reefs and shoals - including an artificial island that was skirted by a U.S. warship this week in a freedom of navigation maneuver that riled Beijing - do generate, or create a claim to, territorial waters and an economic zone. A U.S. ally, the Philippines, contends that they do not.

“The fact that the tribunal did not reject jurisdiction on anything in the case brought by the Philippines, and could end up ruling against it on all these counts, introduces uncertainty and anxiety for China,” said Bonnie Glaser, senior adviser for Asia at the Center for Strategic and International Studies think tank.

Malcolm Cook, senior fellow at the Institute of Southeast Asian Studies in Singapore, said that outside of China, many maritime law experts feel the Philippines has a strong case and are skeptical of the legal basis for China's expansive claims, which it says are rooted in history. China roughly demarcates this vast area on maps with a nine-dash line.

Despite China's latest legal setback, both Glaser and Cook didn't expect it to change course.

“The Chinese navy has a very strong interest in gaining greater sea control over the South China Sea and this interest and its pursuit will likely not be affected by tribunal rulings,” Cook said.

In all, six Asian governments have overlapping claims in the South China Sea, straddling some of the world's busiest sea lanes and in areas with rich fishing grounds and potential undersea oil and gas fields. China's massive construction to transform at least seven shoals and reefs into islands in the disputed Spratly Islands have ratcheted up tensions.

Glaser said China views these waters off its east coast as vital to its security. China needs to control this area to avert any potential crisis intervention by the United States, which since World War II has been the predominant military force in the Asia-Pacific. The ruling Communist Party also needs to be seen as defending national sovereignty.

Since announcing in 2010 that the U.S. has a national security interest in resolving disputes and maintaining peace and security in the South China Sea, Washington has failed to get Beijing to moderate its behavior. In fact, the opposite has happened. When the U.S. called for China and other claimants to halt land reclamation last year, Beijing appeared to double down, building airstrips and other facilities that could have military uses.

Tuesday's sail-by of Subi Reef by the USS Lassen _ following long demands from Congress for action and months of debate within the Obama administration _ was the toughest U.S. step to date to challenge China's island-building.

The guided missile destroyer sailed within 12 nautical miles (22-kilometer) of the reef to underscore Washington's position that the geographic alteration would not allow the previously submerged reef to generate territorial waters. Subi Reef is one of the land features under scrutiny by the tribunal.

Lynn Kuok, a fellow at the Brookings Institution think tank, said the combination of legal pressure and freedom of navigation operations could yet prod Beijing into conforming more to the U.N. convention, even if it does not change its official stance on its South China Sea claims.

“As China grows in strength as a maritime power, Beijing might realize that the country's interests are best protected by upholding rather than undermining the convention,” she said. (AP)