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A stretch of uninhabited, low-lying reefs in the South China Sea is fast becoming a dangerous new flashpoint between China and the Philippines, dealing a setback to recent efforts to de-escalate tensions in one of the world’s most important waterways.

Over the past week, there have been several collisions and confrontations between Chinese and Filipino vessels near Sabina Shoal, a disputed atoll just 86 miles off the west coast of the Philippines and 745 miles from China, which claims almost the entire South China Sea as its sovereign territory despite international rulings to the contrary.

The violence came just weeks after Beijing and Manila reached a temporary agreement to ease tensions over the summer on another nearby reef. China’s increasingly aggressive tactics had raised concerns across the region and also in Washington, a joint defense alliance with the Philippines.

Renewed tensions in the South China Sea are expected to be on the agenda of meetings between U.S. National Security Advisor Jake Sullivan and Chinese Foreign Minister Wang Yi during Sullivan’s visit to China this week.

After a particularly violent clash on the Second Thomas Reef in June, in which Chinese coast guards aimed axes at Filipino soldiers and cut up their rubber dinghies, Chinese and Filipino politicians met for talks and agreed on a de-escalation.

For a while the situation seemed to cool down, but the relaxation was short-lived.

On August 19, coast guard vessels from China and the Philippines collided near Sabina Shoal in the middle of the night. Manila said the Chinese vessels rammed into its ships, leaving a 1.1-meter hole in one vessel and a 90-centimeter gap in another. Beijing blamed the Philippines for the collisions.

Last Sunday afternoon, another clash occurred. The Philippines accused China of ramming a fisheries agency vessel and firing water cannon at it. Eight Chinese vessels collided, including a People’s Liberation Army Navy warship. China said the Philippine vessel “refused to take control” and “deliberately collided with the vessel.”

The following day, another tense standoff erupted. The Philippines said China had deployed “excessive force” of 40 ships – including three People’s Liberation Army warships – to block two Philippine Coast Guard vessels. Beijing said it had taken “control measures” against two Philippine vessels that had “entered” waters near Sabina Shoal.

Analysts say the Sabina Reef is fast becoming the latest confrontation zone in an already highly contested part of the world, where a mistake could quickly escalate into conflict with extremely damaging consequences.

“All signs seem to point to this being an emerging third hotspot,” after the second Thomas Reef and another atoll to the north called Scarborough Reef, said Collin Koh, a research fellow at the S. Rajaratnam School of International Studies in Singapore.

“Manila is trying to prevent a repeat of Scarborough Reef,” which China captured in 2012 after a long standoff with the Philippines and where it has maintained a permanent presence since then, Koh added.

China, on the other hand, is trying to prevent another Thomas Reef, where the Philippines ran a World War II ship aground in 1999 to assert its claim to the reef. Since then, it has stationed a small group of marines there.

The violent clashes around Second Thomas Shoal occurred earlier this summer when Beijing tried to block Manila’s missions to supply its soldiers stationed on the rusting BRP Sierra Madre.

A similar blockade is taking place at Sabina Reef, which is about 40 miles closer to the Philippine coast than the second Thomas Reef. Both lie within the Philippines’ Exclusive Economic Zone (EEZ).

Since April, the Philippines has sent a coast guard ship to Sabina Reef to look for signs of illegal Chinese land reclamation activities. Philippine scientists had previously discovered piles of broken coral on the sandbanks as the presence of Chinese ships in the area increased. China denies the allegations.

With a displacement of 2,300 tons, the 318-foot BRP Teresa Magbanua, anchored in Sabina Shoal, is one of the two largest vessels of the Philippine Coast Guard and its flagship. Acquired from Japan in 2022, it is also one of the newest vessels in Manila’s fleet with a crew of 67.

“This has really angered China and they want the (Philippine) ship gone,” said Ray Powell, director of SeaLight, a maritime transparency project at Stanford University’s Gordian Knot Center for National Security Innovation.

“China calls it a ‘quasi-stranding,’ so they’re basically treating it like it’s a repeat of the Sierra Madre, even though it’s not on the ground, it’s anchored.”

And Beijing has gradually increased the pressure on Manila.

In July, China anchored one of its “monster” coast guard ships, the 12,000-ton CCG-5901, near Sabina Shoal. The CCG-5901 is more than five times the size of the Philippines’ Teresa Magbanua and larger than any other regular coast guard ship in the world.

“Initially, the Chinese were trying to warn Manila to withdraw from Sabina Reef, so they sent the monster ship just to make an impression,” Koh said.

“But the Filipinos sat still and didn’t move at all. I guess the Chinese probably came to a point where they concluded that they need to increase the pressure on the Filipinos and that’s why we’ve seen what’s happened recently.”

In recent weeks, Chinese state media have accused the Philippines of trying to establish a long-term presence at Sabina Reef in order to occupy the reef and suggested that China would not allow resupply missions.

“China will never be deceived by the Philippines again,” the Chinese state news agency Xinhua commented on the dispute on Sunday, referring to the grounding of the Sierra Madre by Manila on the Second Thomas Reef in 1999.

On Monday, the Philippine Coast Guard said it had dispatched two vessels on a “humanitarian mission” to deliver essential food and supplies to its overseas-based personnel on the Teresa Magbanua, including “a special ice cream” in honor of the country’s National Heroes Day.

(Teresa Magbanua, one of the heroines honored on this day, was one of the few women who led Filipino troops in battles against the Spanish colonialists during the Philippine Revolution and against the American forces in the Philippine-American War.)

However, according to the Philippine Coast Guard, the mission failed due to a blockade by 40 Chinese ships.

If China continues to prevent the Philippines from supplying the Teresa Magbanua with food, water and fuel or replacing the crew, the Philippine ship will have to leave, Powell said.

At present, neither Beijing nor Malina seem willing to back down.

“Manila has a lot at stake,” Koh said. “The domestic political circumstances all point to not giving an inch to the Chinese in Sabina Shoal… Marcos Jr. is definitely on the shooting board for that,” he added, referring to Philippine President Ferdinand Marcos Jr.

Since taking office in 2022, Marcos Jr. has strengthened Manila’s alliance with the United States and increasingly challenged China’s expansive claims in the South China Sea, which an international tribunal declared in a landmark ruling in 2016 had no legal basis.

His predecessor, Rodrigo Duterte, a fiery populist who waged a notoriously brutal war on drugs, advocated a much closer relationship with Beijing and was far less willing to confront Beijing on the South China Sea issue.

Manila’s recent “transparency initiative,” aimed at exposing China’s growing power in the disputed waters, has won the city international support, especially from Western countries. But Beijing is not deterred by the negative press, Powell said.

“China appears to be accelerating its plans to control areas in the West Philippine Sea,” he said. “They have the capacity and the will, and they have not seen anything so far that tells them the cost will be too high.”

Meanwhile, both Beijing and Manila are closely monitoring Washington’s reaction.

American officials have repeatedly pledged to protect the Philippines from any armed attack in the disputed waters, stressing Washington’s “ironclad commitment” to a 1951 defense treaty between the two allies.

According to Reuters, Samuel Paparo, commander of the US Indo-Pacific Command, said on Tuesday that American ships could escort Philippine vessels on resupply missions in the South China Sea, calling it a “perfectly reasonable option” but one that would require consultations between the treaty partners.

But it is not in the US interest to be drawn into another global conflict, especially ahead of the presidential election, Koh said, adding that Washington is already preoccupied with the Russian invasion of Ukraine and the raging war between Israel and Hamas in the Gaza Strip.

“The Chinese know that Manila has very limited options if it cannot count on US help,” Koh said. “China is deliberately escalating the situation, probably with the intention of testing the extent to which Washington would support Manila.”