Recent incidents in the South China Sea have increased scrutiny of the Trump administration’s commitment to U.S. allies in the Indo-Pacific. During Donald Trump’s first term, a pause in maritime tensions meant Washington’s obligations were not tested. However, today’s regional environment is far more volatile. Unlike in 2017, Beijing’s coercive behavior in the first part of 2025 has resulted in incidents with Australia and the Philippines, and Manila is pushing back through public exposure and resistance.

As Trump signals interest in a meeting with Xi Jinping, could a transactional foreign policy leave frontline U.S. partners exposed?¹

That prospect has been central to Beijing’s messaging to the region this year. China’s top diplomat, Wang Yi, argued as much at a March 7 press conference during the Two Sessions.² In an unusual broadside against the Philippines — the primary U.S.-allied claimant in the South China Sea — Wang warned that “infringement and provocation will backfire, and those acting as others’ chess pieces are bound to be discarded.”³ Chinese spokespersons have since repeated the line, most recently at a Ministry of National Defense press briefing on April 9.⁴

Trump’s first term fortuitously coincided with a lull in South China Sea tensions: Philippine President Rodrigo Duterte (2016–22) sought Chinese economic assistance, and Beijing restrained its maritime assertiveness in hopes of peeling away a U.S. ally. As a result, the U.S. commitment was not seriously tested.

In contrast, Chinese maritime law enforcement vessels have continually harassed Philippine ships in early 2025, and Manila has actively publicized China’s provocations. This combination of brinkmanship and publicity creates conditions for a serious incident that could put U.S. regional credibility to the test.

On January 24, 2025, Chinese paramilitary law enforcement ships and a low-flying military helicopter forced a scientific team from the Philippine Bureau of Fisheries and Aquatic Resources to abandon a survey at Sandy Cay, near the Philippine outpost on Thitu Island (Pulo ng Pag-asa, 中业岛).⁵ The second-largest of the Spratly Islands, Thitu and its surrounding reefs and sandbars have been the site of repeated confrontations in recent years.⁶ Swarms of Chinese trawlers have lingered in the area, intimidating, surveilling, and disrupting Philippine fishing and supply missions as Manila upgrades Thitu Island’s runway and harbor facilities.⁷ China’s gray-zone operations are sustained by its nearby artificial island at Subi Reef (渚碧礁).

This year’s incident was significantly more coercive than past swarming operations. Videos released by the Philippines showed a China Coast Guard (CCG) ship blocking Philippine survey vessels and a military helicopter hovering at low altitude.⁸ The CCG claimed its vessels had “intercepted, controlled, warned, and expelled” intruding Philippine ships from the area, and state media posted a short video of the incident.⁹ It occurred just four days after Trump’s inauguration and two days after Secretary of State Marco Rubio reaffirmed the United States–Philippines Mutual Defense Treaty, assuring his Philippine counterpart Enrique Manalo of the United States’ “ironclad commitments to the Philippines.”¹⁰ Defense Secretary Pete Hegseth echoed this message during his March visit to Manila.¹¹

An incident involving Australia and China followed on February 11, when Chinese J-16 fighters allegedly dropped flares in front of a Royal Australian Air Force P-8 patrol aircraft near the Paracel Islands.¹² China claims the area as “internal waters” within archipelagic baselines; Australia does not recognize the baselines and asserts that the area is international waters under the United Nations Convention on the Law of the Sea (UNCLOS), with associated rights to navigation and overflight. Defense Minister Richard Marles said the fighter was “so close that there’s no way you could have been able to ensure that the flares did not hit the P-8… Had any of those flares hit the P-8, that would have definitely had the potential for significant damage to that aircraft.”¹³

An even more dangerous encounter occurred on February 19, when a Chinese helicopter flew within three meters of a Philippine patrol aircraft near Scarborough Shoal, according to the Philippine Coast Guard.¹⁴ The Philippines’ maritime agencies are outmatched by the CCG, the world’s largest, but have shown little inclination to back down. President Ferdinand Marcos has emphasized that “not a square inch of Philippine territory is surrendered to any foreign power.”¹⁵

Australia, too, shows little sign of backing off, even as the credibility of U.S. support in the South China Sea wanes. In his 2020 memoir, A Bigger Picture, former Australian Prime Minister Malcolm Turnbull recalled being unsure whether the United States would risk war with China to defend Australia during a freedom of navigation operation (FONOP).¹⁶ Nonetheless, Australia has continued to quietly conduct its own overflights.

The United States, however, appears to have once again paused its program of FONOPs as Trump pursues deals with Xi on trade and fentanyl. In 2017, the first Trump administration likewise placed the existing FONOP program on hold while it engaged with China.¹⁷ At the time of writing, the most recent publicly reported U.S. FONOP in the South China Sea was on December 6, 2024.¹⁸

Because Duterte’s China policies were in basic alignment with the first Trump administration — seeking investment from China and shelving the 2016 UNCLOS arbitration ruling — there were no serious incidents to test U.S. commitment to defend the Philippines. With Marcos as president, the Philippines has actively resisted China’s strategic advances into its exclusive economic zone, shoring up its crumbling outpost at Second Thomas Shoal, briefly staking out a new position at Sabina Shoal, and employing “assertive transparency” to publicize China’s aggression, including through video and social media.¹⁹

But to substantively deal with the problem, the Philippines needs to expand its fleet of maritime law enforcement ships. While the Trump administration may or may not meaningfully assist, Japan, South Korea, and Australia are ready partners. They may view increased Philippine capability in the South China Sea as a strategic counterweight to Beijing’s advances elsewhere in the region.

The Philippines has one further option: to bring the issue to the UN General Assembly (UNGA). As Greg Poling argues, Manila would likely win a UNGA vote over the South China Sea issue.²⁰ There are also signs that states outside the region may be willing to step up as Washington’s commitment comes into question. During a visit to Manila, British Foreign Secretary David Lammy released an unusual video on social media asserting the United Kingdom’s interests in the South China Sea, emphasizing its commitment to UNCLOS — which the United States has not ratified — and criticizing “dangerous and destabilizing activities by China.”²¹

With a more transactional and possibly diminished U.S. presence, more frequent and visible FONOPs by other states are needed to forestall changes to established practices in the region.²² If China-Philippines clashes continue, officials in other capitals must be prepared for a serious incident involving vessel damage or even casualties. Under the Trump administration, the spectrum of possible U.S. responses — ranging from inaction to sudden escalation — is far broader than under previous presidents, injecting new uncertainty into a tense strategic environment.

Escalation could also be a matter of choice. With a slowing Chinese economy, reduced U.S. credibility also increases the potential for China to launch a limited military operation in the South China Sea’s disputed islands that could mobilize its population without the enormous risks of an invasion or blockade of Taiwan.²³ Under previous U.S. administrations, the United Kingdom, Japan, and South Korea would look to Washington’s response to major developments in the region and ensure their own responses were aligned. With Trump as president, countries will need to think more carefully about their own responses to forestall either reckless escalation or unnecessary, and potentially serious, strategic concessions to Beijing.

Endnotes

[1] Ryan Woo, “Pro-Trump Senator Meets China’s Economy Tsar amid Trade Tensions,” Reuters, March 22, 2025, https://www.reuters.com/world/us/us-senator-daines-meets-chinas-vice-pr…; and Keith Bradsher, “Why China Is Wary of a Trump-Xi Summit,” New York Times, March 31, 2025, https://www.nytimes.com/2025/03/31/business/trump-xi-summit-tariffs.html.

[2] “Webinar: Key Takeaways from China’s Two Sessions in 2025,” Asia Society Policy Institute, Center for China Analysis, https://asiasociety.org/policy-institute/webinar-key-takeaways-chinas-two-sessions-2025.

[3] To drive the point home, China’s Ministry of Foreign Affairs released a standalone statement highlighting Wang’s comments.

[4] “Philippines’ Relying on Foreign Support to Make Trouble in South China Sea Will Backfire: Defense Spokesperson,” Ministry of National Defense (People’s Republic of China), press release, April 9, 2025, http://eng.mod.gov.cn/xb/News_213114/NewsRelease/16379706.html.

[5] Jim Gomez, “Philippines Accuses China’s Forces of Harassing Fisheries Vessels in the South China Sea,” Associated Press, January 25, 2025, https://apnews.com/article/south-china-sea-sandy-cay-philippines-606e46….

[6] “Tension Rises Between Beijing, Manila over Disputed Reefs,” Benar News, March 22, 2024, https://www.benarnews.org/english/news/philippine/waterway-tension-0322….

[7] Jim Gomez, “Manila Protests ‘Swarming’ Chinese Boats near Island,” Navy Times, April 1, 2019, https://www.navytimes.com/news/your-navy/2019/04/01/manila-protests-swa…; and Sam Beltran, “Philippines Outnumbered as ‘Largest China Vessel Swarm’ Spotted near Thitu Island,” South China Morning Post, December 2, 2024, https://www.scmp.com/week-asia/politics/article/3288805/philippines-out….

[8] “Philippines Suspends South China Sea Science Mission After China ‘Harassment,’” Benar News, January 27, 2025, https://www.benarnews.org/english/news/philippine/philippines-china-san….

[9] “中国海警局新闻发言人就菲侵闯铁线礁发表谈话” [China Coast Guard Spokesperson Remarks on the Philippines' Intrusion into Sandy Cay], China Coast Guard, January 25, 2025, https://www.ccg.gov.cn/wqzf/202501/t20250125_2602.html; and “现场视频: 菲律宾登铁线礁被我海警拦下” [On-Site Video: The Philippines Landed on Sandy Cay and Was Stopped by Our Coast Guard], CCTV, video, January 26, 2025, https://news.cctv.com/2025/01/26/ARTIAxikhOlrCek5gplxwU0u250126.shtml.

[10] “Secretary Rubio’s Call with Philippine Secretary of Foreign Affairs Manalo,” U.S. Department of State, press release, January 22, 2025, https://www.state.gov/secretary-rubios-call-with-philippine-secretary-o….

[11] Matthew Olay, “Hegseth Says U.S., Philippines Agree on Plan to Reestablish Deterrence in Indo-Pacific,” U.S. Department of Defense, March 28, 2025, https://www.defense.gov/News/News-Stories/Article/article/4138090/hegse….

[12] “China Says Australia ‘Spreading False Narratives’ and ‘Stirring Up Trouble’ After South China Sea Incident,” ABC News (Australia), February 14, 2025, https://www.abc.net.au/news/2025-02-15/china-hits-back-at-australia-aft….

[13] “Australia Protests to China About ‘Unsafe’ Aircraft Maneuver over Paracels,” Benar News, February 14, 2025, https://www.benarnews.org/english/news/philippine/south-china-sea-chine….

[14] “Chinese Navy Helicopter Flies ‘Dangerously’ Close to Philippine Plane,” BBC, video, February 18, 2025, https://www.bbc.com/news/videos/cvgdrqgxyg3o.

[15] Micah McCartney, “Video Shows U.S. Ally Challenging Chinese Presence near Coast,” Newsweek, March 10, 2025, https://www.newsweek.com/philippines-china-coast-guard-south-china-sea-….

[16] Malcolm Turnbull, A Bigger Picture (Melbourne: Hardie Grant, 2020).

[17] Andrew Chubb, “South China Sea Patrols: Does the Trump Team Get It?” Lowy Institute, Interpreter, August 15, 2017, https://www.lowyinstitute.org/the-interpreter/south-china-sea-patrols-d…; and “President Trump at Mar-a-Lago Dinner Table with Chinese President Xi Jinping (FNN),” LiveNOW from Fox, YouTube video, April 6, 2017, https://www.youtube.com/watch?v=wMVwnzJTrx4.

[18] “7th Fleet Conducts Freedom of Navigation Operation,” Commander of the U.S. Pacific Fleet, press release, December 6, 2024, https://www.cpf.navy.mil/Newsroom/News/Article/3987553/7th-fleet-conduc….

[19] Edcel John A. Ibarra and Aries A. Arugay, “Something Old, Something New: The Philippines’ Transparency Initiative in the South China Sea,” Fulcrum, May 6, 2024, https://fulcrum.sg/something-old-something-new-the-philippines-transpar….

[20] Gregory B. Poling, “How to Slay a Giant: Reviving the South China Sea Arbitration,” Center for Strategic and International Studies, January 10, 2025, https://www.csis.org/analysis/how-slay-giant-reviving-south-china-sea-a….

[21] David Lammy, “We Are Concerned by Dangerous and Destabilising Activities by China in the South China Sea,” X, video, March 10, 2025, https://x.com/DavidLammy/status/1899050138003198021.

[22] Isaac B. Kardon, China’s Law of the Sea: The New Rules of Maritime Order (New Haven: Yale University Press, 2023).

[23] Andrew Chubb, “Taiwan Strait Crises: Island Seizure Contingencies,” Asia Society Policy Institute, Center for China Analysis, February 22, 2023, https://asiasociety.org/policy-institute/taiwan-strait-crises-island-se….