With a successful Group of 20 summit under its belt and the run-up to November’s presidential election occupying Washington, Beijing appears to be testing the waters for a potential move on a hotly disputed site in the South China Sea that would further extend its grip there — and significantly ratchet up tensions in the region.

China has in recent days and weeks ramped up its activity around the Scarborough Shoal, with Philippines’ Defense Ministry releasing pictures Wednesday showing what it said were Chinese boats near the chain of rocks and reefs just 230 km (140 miles) from the Philippine coast. The release came just hours before Southeast Asian nations were due to meet China’s premier at a summit of Southeast Asian leaders in Laos.

The moves have stoked fears in Manila that Beijing could be laying the groundwork for an eventual land-reclamation project at the contentious collection of rocky outcroppings that barely jut above water at high tide.

China’s focus in the contentious waters has shifted since the Permanent Court of Arbitration in The Hague issued a ruling in July that invalidated its claims to the South China Sea, a decision Beijing has lambasted as “waste paper.”

Starting in 2014, China began employing an army of dredging vessels to create seven man-made islands in the South China Sea’s Spratly chain, building military-grade airstrips, radar facilities and hangers for Chinese fighter jets on a number of the reclaimed islets, including Mischief Reef, located 250 km west of the Philippines’ Palawan Island.

It has also beefed-up the defense capabilities on Woody Island, its main outpost in the Paracel archipelago further west, deploying surface-to-air missiles and fighter jets there in February.

But experts say Scarborough Shoal would be the crowning jewel in a bid to solidify an iron grip over the South China Sea.

‘Strategic triangle’

Building at Scarborough would create a large “strategic triangle” comprising Woody Island and its Spratly outposts, giving Beijing the ability to police an air defense identification zone (ADIZ) in the South China Sea.

The impact of such a strategic triangle would be tremendous for both the United States’ and Japan’s strategic planning, some experts say, and could be a game-changer in regional power relations.

“If China is successful in militarizing the Scarborough Shoal, this would represent a significant change in the status quo,” said Jeffrey Hornung, a security and foreign affairs expert with the Sasakawa Peace Foundation USA in Washington.

“Should China build up the shoal with radars, missiles and an airstrip, it would enhance China’s anti-access, area-denial (A2/AD) capabilities as well as improve its power-projection capabilities in the region, particularly vis-a-vis the U.S.”

Hornung said this matters because a new base that forms a strategic triangle with its facilities and runways in the Paracels and Spratlys would bring the entire region under Chinese radar, missile and air coverage — effectively creating a “Chinese lake.”

“This would enable China to control the sea lines of communication, monitor foreign naval and air activities, enforce a South China Sea air defense identification zone and could work to blunt America’s freedom of action in times of conflict.

Hornung also said Japan, like the U.S. and others, is concerned about this because this gives China a significant edge not just in a wartime situation, but in peacetime as well, and will enable it to better monitor what the U.S. and its allies are doing in the region.

Key flash point

Media reports have repeatedly mentioned Scarborough as a key flash point.

China was prepared to initiate land-reclamation at Scarborough in March, according to a Financial Times report citing current and former U.S. officials, but backed down after U.S. President Barack Obama warned Chinese leader Xi Jinping of serious consequences if it began dredging work there.

Another report, this one coming just last month by the South China Morning Post, reignited concern over the issue. It quoted an unidentified source familiar with the Scarborough matter as saying that reclamation work there would not start until after the Group of 20 summit, which wrapped up Monday in the Chinese host city of Hangzhou, but potentially before the U.S. presidential election on Nov. 3.

“U.S. President Barack Obama will focus on domestic issues ahead of the election as he needs to pass down legacies before leaving office. That might make him busy and he might not have time to take care of regional security issues,” the source was quoted as saying.

The Hong Kong-based daily had earlier reported in late April that Chinese work at the shoal would begin within the year.

The Philippines, a U.S. treaty ally, first said last week that it had spotted Chinese barges and numerous other vessels — including Chinese coast guard ships — at Scarborough. It said these sightings could presage a move to turn the shoal into another man-made island.

State Department spokesperson Katina Adams told The Japan Times this week that it was aware of reports that the Philippines has raised concerns about the number of Chinese vessels near Scarborough.

“We continue to closely monitor the situation around Scarborough Reef, and we encourage all sides to exercise restraint and take practical steps to lower tensions,” Adams said.

Lightning advance?

Jay Batongbacal, who heads the Institute for Maritime Affairs and Law of the Sea at the state-run University of the Philippines, said the vessels seen last week could allow China to make a lightning advance on Scarborough.

“Rather than barges as widely reported, they do appear to be at least one dredging ship and a cable-laying ship,” Batongbacal told The Japan Times. “These could be for preparatory work. the dredger could be used to create deeper channels into/within the reef for subsequent construction activities. The cable laying ship could be intended to lay communications cables that would be more secure than satellite/radio links.

“Both could allow sudden massive reclamation in a single burst of activity, as soon as the weather permits,” he said, adding that a cable-laying ship could also be used to lay a series of listening devices across the seafloor all the way up to the mainland that would be effective against submarines and surface ships.

‘Maritime militia’

Regional security experts also said some of the vessels spotted by Manila were likely part of China’s “maritime militia,” or “little blue men,” the sea equivalent of Russian leader Vladimir Putin’s “little green men” that were deployed during Moscow’s annexation of Crimea.

The nominally civilian maritime militia — which China also used last month to swarm the waters near the Japanese-controlled, Chinese-claimed Senkaku Islands in the East China Sea — is one of Beijing’s most important tools. Often masked as innocuous fishing vessels, the militia is employed in “gray zone” activities as a tool of asymmetric warfare, offering major rewards while threatening the U.S., Japan and other potential opponents with major risks if engaged, observers say.

“It is very likely that at least a portion of these vessels (near Scarborough) are maritime militia, given that they do not seem to be engaged on purely private economic activities,” said Alex Calvo a guest professor at Nagoya University focusing on security issues. He said the vessels in the area of Scarborough could either be manned by militia members and formally affiliated with the organization or simply one with all or some crew belonging to it, perhaps sporting high-tech equipment provided by Chinese authorities.

Permanent presence

China’s Foreign Ministry said Wednesday that there had been no change to the situation around Scarborough.

“I can tell you that there has not been any change to the Huangyan Island situation. China has also not taken new actions,” spokeswoman Hua Chunying told a daily news briefing in Beijing, using China’s name for the shoal.

Philippine President Rodrigo Duterte was set to ask Chinese Premier Li Keqiang at Wednesday’s summit whether the vessels were on another island-making mission on the Scarborough, just a few hundred kilometers from Philippine military bases hosting U.S. troops.

Bonnie Glaser, a regional security expert at the Center for Strategic and International Studies think tank in Washington, said the distance from Scarborough to the bases was a top concern for the U.S. and the Philippines. Manila is a U.S. treaty ally and a deal between the two countries allowing an increased American military presence in the former U.S. colony was greenlighted in January.

“I think the main concern is the proximity of Scarborough Shoal to the Philippines main island,” Glaser said. “The U.S. will be rotating forces out of bases in the Philippines and a Chinese military outpost on Scarborough will pose a threat to these assets.”

According to retired U.S. Marine Col. Grant Newsham, a senior research fellow at the Japan Forum for Strategic Studies in Tokyo, China would effectively have a permanent presence there under such a scenario.

“This is a huge military advantage,” Newsham said. “U.S. ships and aircraft may be able to operate in and transit the South China Sea, but it is an ephemeral presence — here today, gone tomorrow. The Chinese will be there regardless — and that is what matters.”

Move imminent?

While major Chinese dredging operations in the South China Sea have apparently been halted since the end of last year, a number of observers described a move on Scarborough as seemingly imminent.

“Right now it is still unclear, but I would not really be surprised,” said Nagoya University’s Calvo. “China is indeed ready to cross that ‘red line,’ among other reasons because it is not much of a red line. It is not backed by any explicit threat to use force.”

Philippine Supreme Court Senior Associate Justice Antonio Carpio, a vocal defender of Manila’s territorial claims in its dispute with Beijing, offered a more clear-cut view.

“My personal assessment is that China will start the dredging after the G-20 meeting and before the November elections in the U.S.,” Carpio told The Japan Times.

He said Beijing has long planned to militarize the Spratlys and Scarborough Shoal so as to enforce its so-called “nine-dash line” claim to most of the South China Sea.

“The Chinese have built islands on all the seven reefs that China occupies in the Spratlys,” Carpio said. “There is no reason why Scarborough Shoal, strategically located near the Bashi Channel — the shortest outlet of China’s Hainan-based nuclear missile submarines to the Pacific Ocean, will be an exception.”

Abhijit Singh, head of the Maritime Policy Initiative Observer Research Foundation think tank in New Delhi, said for the Chinese, the only issue was the timing.

“My sense is that it may not happen in the next few weeks, but at an opportune moment in days following, when China can justify its reclamation by pointing to a U.S. provocation,” Singh said. “But I have little doubt that the Chinese will ultimately build a structure on Scarborough, because it’s the last link in the regional maritime strategy.”

With ramped-up military activity in the waters recently, including U.S. “freedom of navigation” patrols near Chinese-held islands and regular Chinese air force “combat patrols” in the area, the potential for an unintended clash — something that could be seen as an “opportune moment” — is high.

Psychological war

But regardless of any Chinese move on Scarborough, the mere psychological effects of the issue could also prove destabilizing.

“The psychological threat of China dominating such a strategic area has many worried that China will control the South China Sea, and all the trade that transits through it,” said Sasakawa’s Hornung. “This, in turn, has led regional countries like Japan to look with concerned eyes to the U.S. should the dredging start.

To date, the U.S. has opposed Chinese actions in the South China Sea. But beyond the occasional patrol or limited efforts to bolster regional nations maritime capabilities, the U.S. response has essentially been limited to diplomatic protests and the building of a coalition opposed to Chinese actions.

“Because the Philippines is a treaty ally of the U.S., if China can act freely with no U.S. response beyond a diplomatic protest, its credibility as an ally will be under severe stress,” said Hornung. “In particular, a non-U.S. response would send shock waves through Tokyo, given that concerns over U.S. commitment to the defense of the Senkaku Islands continues to lurk among officialdom in Tokyo.”

“If China starts to dredge, it behooves the U.S. to act firmly, knowing that its response will be under close scrutiny from its regional allies.”