BEIJING >> China has intensified the drumbeat of its opposition to an international tribunal’s ruling expected Tuesday that could threaten its expansive claims in the South China Sea.

How Beijing responds to the ruling in the case filed by U.S. ally the Philippines could chart the course of global power relations in an increasingly dangerous hotspot. It comes as the U.S. has ramped up its military presence in the region and could seek to marshal world opinion to pressure Beijing into complying with the verdict. A new Philippine leader who appears friendlier to Beijing could also influence the aftermath of the ruling.

The Hague-based tribunal will decide on the 2013 case that challenges the so-called nine-dash line that China uses to claim virtually the entire South China Sea and which Manila opposes because it infringes upon its own 200-mile exclusive economic zone. The dispute centers on waters through which an estimated $5 trillion in global trade passes through each year and are home to rich fishing stocks and a potential wealth of oil, gas and other resources.

The Philippines has also asked the tribunal to rule on whether several disputed areas are outcrops, reefs or islands, a move aimed at clarifying the extent of territorial waters they are entitled to or if they can project exclusive economic zones.

More than merely about the sovereignty over the rocks and reefs or the actual waters, the South China Sea dispute has become a testing ground for a rising China to challenge the U.S.’s leadership in the Asian strategic order, analysts say.

Beijing wants to use this dispute to show how “China’s own growing maritime power and its economic significance to the United States and the global economy have reached the point where the United States can no longer afford to stand up to China,” said Hugh White, professor of strategic studies at The Australian National University. “That calculation might prove to be wrong.”

China has boycotted the case, arguing that the tribunal has no jurisdiction and saying it won’t accept the ruling. It has insisted that bilateral talks between Beijing and other claimants is the only way to address the dispute.

Some experts have speculated that China could respond to an unfavorable ruling by establishing an air defense identification zone over all or part of the South China Sea. There is similar speculation that China might militarize a reef off the Philippine coast, the Scarborough Shoal, where a standoff with China prompted the Philippines to initiate the tribunal case in 2013. Beijing has given no direct indication of a tougher response, saying it remains committed to bilateral negotiations with Manila.

Tuesday’s ruling might further pressure China to clarify what exactly it is claiming with its “nine-dash line” boundary.

Findings of the tribunal are binding on the parties, including China. But the court – without police or military forces or a system of sanctions at its disposal – can’t enforce its ruling, so its potential impact remains unclear.

Still, in recent weeks, China has spared no effort to denounce the proceedings as unlawful, publishing state media commentaries and deploying senior military officers, current and former top officials and academics to relentlessly convey Beijing’s opposition. On Monday, the day before the verdict, the overseas edition of the ruling Communist Party’s mouthpiece, the People’s Daily, urged the Philippines to return to talks with China and the U.S. to stay out of the dispute.

The arbitration outcome, known as an “award,” was dismissed by former Chinese state councilor Dai Bingguo, in a conference in Washington, D.C., last week, as “nothing more than a piece of paper.”

Beijing has faced mounting calls to observe international law. At a U.S. congressional hearing last week, Abraham Denmark, deputy assistant secretary of defense for East Asia, urged both parties to comply with the ruling. Denmark said it was a chance to determine whether the region’s future will be defined by adherence to international laws or by “raw calculations of power.”

China might use strong rhetoric but not take aggressive action to avoid having the topic dominate the agenda at upcoming multilateral forums, said Bonnie Glaser, senior adviser for Asia at the Center for Strategic and International Studies in Washington, D.C.

Glaser said Chinese officials she’s spoken to say privately they hope the case would not rule entirely in the Philippines’ favor so that Beijing can say in internal discussions that Chinese interests have not been “irreparably harmed.”

A key factor that could change the equation of the consequences of this ruling is how the Philippines’ new President Rodrigo Duterte decides to respond. His predecessor Benigno Aquino III’s government filed the case, straining Manila’s relations with Beijing, but Duterte has shown readiness to mend frosty ties with China.

While Duterte has made critical remarks against the U.S., he has pointed out the benefits of nurturing friendly relations with Beijing, including a Chinese offer of financing railway projects in the Philippines. Duterte’s rise has given China an opening to make inroads in one of America’s closest security allies.

Last week, Duterte said his government stood ready to talk to China if it gets a favorable ruling. “When it’s favorable to us, let’s talk,” he said. “We are not prepared to go to war, war is a dirty word.”

It remains to be seen, however, how far Duterte can stray from Manila’s critical stance on China’s territorial assertiveness, given his country’s close ties with the U.S. and growing nationalist sentiment against China’s actions.

Jay Batongbacal, an expert on South China Sea issues at the state-run University of the Philippines, said the government should avoid revealing its cards ahead of potential negotiations with Beijing, “otherwise you lose the leverage that you have.”

Left-wing activists protested at the Chinese consulate in metropolitan Manila on Monday, urging China to leave what they said were other countries’ territories.

“We’re calling on our brothers in Southeast Asia that this call for a ‘Chexit,’ or China exit, now is not only for Filipinos but for all to call on China to respect our territorial integrity,” said protest leader Mong Palatino.

U.S. Defense Secretary Ash Carter called his Philippine counterpart, Delfin Lorenzana, Monday to reaffirm the strength of their countries’ decades-long treaty alliance. They discussed the arbitration issue “and agreed to consult closely as the ruling is announced,” according to a statement issued by the Philippine Department of National Defense.

Experts say the outcome of the dispute could provide ammunition for other countries involved in disputes with China. Six governments have overlapping territorial claims in the South China Sea – China, Vietnam, the Philippines, Taiwan, Malaysia and Brunei. In addition, China’s nine-dash line overlaps waters that are part of Indonesia’s internationally recognized exclusive economic zone.

“This is a time for China not to keep pushing forward too aggressively because they could embolden Vietnam and Indonesia to file a case as well,” Glaser said.

Regardless, the ruling is unlikely to stop China from continuing to pursue more effective control over the sea space and airspace of the South China Sea, Glaser said.

Over the last few months, the U.S. has held combined exercises by two Navy aircraft carrier strike groups off the coast of the Philippines and freedom of navigation cruises near China’s man-made islands to assert its presence in the Western Pacific. Chinese state media have accused Washington of trying to turn the South China Sea “into a powder keg” and warned it not to underestimate China’s determination to defend its territorial claims.

Chinese warships, fighter jets and submarines have held live-fire war games as part of what the People’s Liberation Army Navy called routine exercises in the week running up to the tribunal’s ruling, drills that were seen at least in part responding to the U.S. presence.

“There’s a real game of nerves going on here with China perhaps assuming that the U.S. is bluffing and the U.S. hoping that China will actually not test American resolve,” Australian National University’s White said.

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Gomez reported from Manila, Philippines. Teresa Cerojano contributed reporting in Manila.