US officials are worried that an upcoming international court ruling pertaining to a case brought by the Philippines against China over its South China Sea claims could compel Beijing to declare an air defense identification zone, or ADIZ, over the region.

The United States has been pressuring Asian and other countries to support the judges' statement that their ruling must be binding.

US Secretary of State John Kerry

“We would consider an ADIZ...over portions of the South China Sea as a provocative and destabilizing act which would automatically raise tensions and call into serious question China's commitment to diplomatically manage the territorial disputes of the South China Sea,” Kerry Sunday said during a visit to Mongolia.

“So we urge China not to move unilaterally in ways that are provocative,” added Kerry, who will visit China after Mongolia.

China imposed an ADIZ over the East China Sea in 2013, requiring that aircraft identify themselves to Chinese authorities above the area.

However, Beijing has refused to deny it plans to declare such a zone for the South China Sea again, but said any move would depend on the threat level, asserting that it reserved the right to set one up.

Washington accuses China of extending its military reach in the South China Sea and unnerving its neighbors by developing man-made islands which could house military airfields and weapons systems.

This US Navy photo obtained February 1, 2016 shows the Arleigh Burke-class guided-missile destroyer USS Curtis Wilbur as it conducts a live fire gunnery exercise in the South China Sea on January 15, 2016. (Via AFP)

On Saturday, Defense Secretary Ashton Carter said the US will remain the most powerful military and the main guarantor of regional security, while offering closer cooperation with Beijing to establish a “principled security network” across the Asia Pacific.

“There is growing anxiety in this region, and in this room, about China’s activities on the seas, in cyberspace, and in the region’s airspace.”

China said last month that frequent US Navy patrols in the South China Sea were forcing Beijing to boost its defense capabilities in the area.

The Chinese Defense Ministry said it deployed two navy fighter jets, one early warning aircraft, and three ships to warn off the destroyer USS William P. Lawrence.

The South China Sea has become a source of tension between China, the US, and some other regional countries, who are seeking control of trade routes and mineral deposits there.

China has on different occasions asserted its sovereignty over the sea, parts of which are also claimed by Brunei, Malaysia, Taiwan, Vietnam and the Philippines.

Beijing accuses Washington of meddling in the regional issues and deliberately stirring up tensions in the disputed waters.

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