President Obama and Chinese President Xi Jinping during a joint news conference at the White House in September. (Andrew Harnik/Associated Press)

The Obama administration is moving toward what could be a dangerous showdown with China over the South China Sea.

The confrontation has been building for the past three years, as China has constructed artificial islands off its southern coast and installed missiles and radar in disputed waters, despite U.S. warnings. It could come to a head this spring, when an arbitration panel in The Hague is expected to rule that China is making “excessive” claims about its maritime sovereignty.

What makes this dispute so explosive is that it pits an American president who needs to affirm his credibility as a strong leader against a risk-taking Chinese president who has shown disregard for U.S. military power and who faces potent political enemies at home.

“This isn’t Pearl Harbor, but if people on all sides aren’t careful, it could be ‘The Guns of August,’ ” says Kurt Campbell, former assistant secretary of state for Asia, referring to the chain of miscalculations that led to World War I. The administration, he says, is facing “another red line moment where it has to figure out how to carry through on past warnings.”

What troubles the White House is that President Obama thought he was assured by President Xi Jinping in Washington in September that China would act with restraint in the South China Sea. “China does not intend to pursue militarization,” Xi said publicly in the Rose Garden.

China’s recent moves appear to contradict these assurances. Administration officials point to China’s installation of surface-to-air missiles on Woody Island in the Paracel chain in February and its recent installation of military radar systems on Cuarteron Reef , one of the artificial islands it has created hundreds of miles from its coast.

Obama cautioned in November against such provocative actions, telling an Asia-Pacific economic summit: “We agree on the need for bold steps to lower tensions, including pledging to halt further reclamation, new construction and militarization of disputed areas in the South China Sea.”

China has largely ignored such warnings, and the administration’s problem now is how to assure Southeast Asian allies that it is not passive about the Chinese threat, while avoiding open military conflict. The U.S.-China breach could widen when Obama and Xi meet March 31 at the Nuclear Security Summit in Washington.

One trigger for escalation could be China’s response to the forthcoming ruling by the arbitration panel in The Hague in a case brought by the Philippines in 2013. The Philippines argued that China was making an “excessive claim” to nearly all the South China Sea by asserting what it calls the “nine-dash line,” based on old maps and claims. The panel will probably issue its ruling in April or May, and Campbell and other knowledgeable experts predict that it will carefully validate the Philippine position.

What will China do next? Beijing has denounced such arbitration of its maritime claims, and some U.S. officials believe it may respond to an unfavorable ruling by declaring an air-defense identification zone, or “ADIZ,” in the South China Sea — in effect banning flights there without Chinese permission. This would present a new and dangerous provocation for Washington.

The Pentagon argues that the United States should immediately challenge any air-defense identification zone claim by flying U.S. military planes into the area. That’s what happened in November 2013 when B-52s immediately challenged an ADIZ declared by China in the East China Sea. Because this overflight had previously been scheduled, the Pentagon didn’t have to ask White House approval; Pentagon officials fear that if such permission had been required, it would have been denied.

This time, the White House has an intense interagency planning process underway to prepare for the looming confrontation. Options include an aggressive tit-for-tat strategy, in which the United States would help countries such as the Philippines and Vietnam build artificial islands of their own in disputed waters. The Philippines effectively took such a step in 1999 when it deliberately grounded a large vessel on a shoal in the Spratly Islands; it recently resupplied that vessel, while U.S. drones patrolled overhead.

Campbell contends that the wisest course for the United States would be to work with other Southeast Asian nations to challenge Chinese claims. This might include planes and ships from Australia, Singapore, India and European countries, for example.

“You don’t want the Chinese to lose face,” says Campbell. “But you want their leadership to understand that if they continue along this path, they risk spiraling the relationship into a very negative place.”

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