Vietnam is on a South China Sea island-building binge that will likely see it soon surpass the area China has reclaimed in the strategic and contested Spratly Islands, according to a new report from the Asia Maritime Transparency Initiative.
Since the start of 2025, Hanoi has been dredging and adding surface area to eight features it controls in the island chain in the southeastern quarter of the South China Sea, said the AMTI report, based on satellite imagery from MAXAR and Planet Labs.
The Spratly Island chain consists of more than 100 small islands or reefs and is claimed in full by China, Vietnam and Taiwan with partial claims by the Philippines, Malaysia and Brunei, according to the CIA World Factbook.
China’s claims have drawn headlines for more than a decade, as Beijing has reclaimed land at several features, building runways and military installations to solidify its positions. Its building of fortifications came despite leader Xi Jinping in telling then-US President Barack Obama in 2015 that it had no plans of doing so.
Beijing claims almost all of the 1.2 million-square-mile South China Sea, through which trillions of dollars in global trade passes annually, as its sovereign territory. It bases that claim on its so-called Nine Dash Line, which the Permanent Court of Arbitration in the Hague has previously ruled has no legal basis.
Vietnam’s claims have not been as outspoken as China’s and its previous reclamation efforts less ambitious.
Some of the reefs where island-building is now going full tilt have long been held by just small pillboxes, including Alison Reef, Collins Reef, East Reef, Landsdowne Reef and Petley Reef, according to the AMTI, which is a project of the Center for Strategic and International Studies (CSIS). New land is also being constructed at three features that were built up in earlier rounds of reclamation – Amboyna Cay, Grierson Reef and West Reef – the AMTI report said.
“All 21 Vietnamese-occupied rocks and low-tide elevations in the Spratly Islands have now been expanded to include artificial land,” AMTI said.
“As of March 2025, Vietnam had created about 70 percent as much artificial land in the Spratlys as China had. Reclamation at these eight new features all but ensures that Vietnam will match—and likely surpass—the scale of Beijing’s island-building,” the report said.
Those 21 features under Hanoi’s control compare to just seven under Beijing’s, according to AMTI.
Meanwhile, on seven other Vietnamese-controlled islands where reclamation work has largely been completed, military-related structures, including munitions depots, have been or are being built, according to the report.
Tensions, clashes
The new report comes amid a spike in tensions between China and the Philippines over South China Sea territory.
Competing claims by Beijing and Manila have become increasingly contentious in the past few years, including violent clashes between their coast guards with water cannons and, in one case, bladed weapons. That clash in the Spratlys near Second Thomas Shoal, on which Philippine marines are stationed in a rusting World War II naval vessel, left a Filipino crewman missing a thumb.
Last month, north of the Spratlys near Scarborough Shoal, a Chinese navy destroyer collided with a China Coast Guard ship as the two harassed a Philippine Coast Guard vessel in contested waters. Images showed heavy damage to the bow of the China Coast Guard ship.
The China-Philippines flare-ups may have provided Vietnam with excellent cover for its move to build up the islands it controls, analysts said.
“For now much of China’s bandwidth of attention is directed at the Philippines, and it would rather maintain a stable front with each of the other Southeast Asian rivals in the South China Sea,” said Collin Koh, a research fellow at the S. Rajaratnam School of International Studies (RSIS) in Singapore.
Ray Powell, director of SeaLight, a maritime transparency project at Stanford University’s Gordian Knot Center for National Security Innovation, echoed Koh’s comments.
“It seems that Beijing has calculated that keeping the Philippines isolated from the other South China Sea claimants is worth more right now than preventing Vietnam from making substantial territorial gains,” Powell said.
“Hanoi may owe Manila a debt of gratitude, since it’s hard to see how this could have happened if Beijing hadn’t been so preoccupied with the problem to the east,” Powell said, adding that, “China has been remarkably muted about Vietnam’s island-building campaign.”
That was reflected in Beijing’s official reaction to the AMTI report.
“The Spratly Islands are China’s inherent territory. China firmly opposes relevant countries’ construction activities on illegally occupied islands and reefs. China will take necessary measures to safeguard its territorial sovereignty and maritime rights and interests,” Foreign Ministry spokesperson Guo Jiakun told a regular press briefing Monday.
Vietnam and the Philippines did not comment on the AMTI report when asked by CNN.
Past disagreements between China and Vietnam over South China Sea territory have resulted in bloodshed, including in 1974 when a South Vietnamese naval vessel was sunk and 53 South Vietnamese troops killed in a battle with Chinese forces over the Paracel Island chain in the northwestern part of the South China Sea.
Beijing has maintained a big edge in the South China Sea since, and Koh said it may not find Hanoi’s latest moves to be overly threatening.
“China commands a yawning gap in mobile military and coast guard assets – hence this probably explains why Beijing is not deemed to be alarmed enough to do anything to stop Hanoi,” he said.
But he cautioned Beijing must not overestimate that advantage, noting that Vietnam and the Philippines enjoy improving relations.
“There’s been effort between Vietnam and the Philippines to come closer on maritime security cooperation, as evidenced by the recent bilateral coast guard exchanges and joint exercise. That should serve as a timely reminder to Beijing that Hanoi owns the Manila card of leverage,” Koh said.
CNN’s Yong Xiong contributed to this report.
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