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Updated December 19, 2022
China Primer: South China Sea Disputes
Overview
defining the scope of its “adjacent waters” claim. On maps,
Multiple Asian governments assert sovereignty over rocks,
China depicts its claims with a “nine-dash line” (see Figure
reefs, and other geographic features in the heavily
1) that, if connected, would enclose an area covering
trafficked South China Sea (SCS), with the People’s
approximately 62% of the sea, according to the U.S.
Republic of China (PRC or China) arguably making the
Department of State. (The estimate is based on a definition
most assertive claims. The United States makes no
of the SCS’s geographic limits that includes the Taiwan
territorial claim in the SCS and takes no position on
Strait, the Gulf of Tonkin, and the Natuna Sea.) China has
sovereignty over any of the geographic features in the SCS,
never explained definitively what the dashed line signifies.
but has urged that disputes be settled without coercion and
on the basis of international law. Separate from the
Figure 1. The South China Sea
sovereignty disputes, the United States and China disagree
over what rights international law grants foreign militaries
to fly, sail, and operate in a country’s territorial sea or
Exclusive Economic Zone (EEZ).
Since 2013, the sovereignty disputes and the U.S.-China
dispute over freedom of the seas for military ships and
aircraft have converged in the controversy over military
outposts China has built on disputed features in the SCS.
Observers viewed the military outposts as part of a PRC
effort to project military power eastward from its coast and
contest U.S. military supremacy in maritime East Asia.
Much of China’s military modernization is aimed at
developing capabilities to deter or defeat third-party
intervention in a regional military conflict. (For more on
China’s military, see CRS In Focus IF11719, China
Primer: The People’s Liberation Army (PLA), by Caitlin
Campbell.) Observers have been alert to other actions
China might take to dominate the SCS, including initiating
reclamation on another SCS geographic feature, such as
Scarborough Shoal, or declaring an Air Defense
Source: CRS graphic.
Identification Zone (ADIZ) over parts of the SCS.
In the northern part of the SCS, China, Taiwan, and
The last several Congresses have focused on China’s efforts
Vietnam contest sovereignty of the Paracel Islands; China
to use coercion and intimidation to increase its influence,
has occupied them since 1974. In the southern part of the
including in the SCS, and passed legislation aimed at
sea, China, Taiwan, and Vietnam claim all of the
improving the ability of the United States and its partners to
approximately 200 Spratly Islands, while Brunei, Malaysia,
protect their interests and freedom of navigation and
and the Philippines, a U.S. treaty ally, claim some of them.
oversight.
Vietnam controls the greatest number. In the eastern part of
the sea, China, Taiwan, and the Philippines all claim
Key Facts
Scarborough Shoal; China has controlled it since 2012.
The SCS is one of the world’s most heavily trafficked
China’s “nine-dash line” and Taiwan’s similar “eleven-dash
waterways. An estimated $3.4 trillion in ship-borne
line” overlap with the theoretical 200-nautical-mile (nm)
commerce transits the sea each year, including energy
EEZs that five Southeast Asian nations—Brunei, Indonesia,
supplies to U.S. treaty allies Japan and South Korea.
Malaysia, the Philippines, and Vietnam—could claim from
According to the U.S. Energy Information Administration,
their mainland coasts under the 1994 United Nations
the SCS contains about 11 billion barrels of oil rated as
Convention on the Law of the Sea (UNCLOS). Indonesia
proved or probable reserves—a level similar to the amount
disputes China’s assertions of maritime rights near its coast.
of proved oil reserves in Mexico—and 190 trillion cubic
Dispute over Freedom of the Seas
feet of natural gas. The SCS also contains significant fish
stocks, coral, and other undersea resources.
A dispute over how to interpret UNCLOS lies at the heart
of tensions between China and the United States over the
The Sovereignty Disputes
activities of U.S. military vessels and planes in and over the
China asserts “indisputable sovereignty over the islands in
SCS and other waters off China’s coast. The United States
the South China Sea and the adjacent waters” without
and most other countries interpret UNCLOS as giving
coastal states the right to regulate economic activities
https://crsreports.congress.gov
China Primer: South China Sea Disputes
within their EEZs, but not the right to regulate navigation
territorial sea; three of the Spratlys features that China
and overflight through the EEZ, including by military ships
occupies generate no entitlement to maritime zones; and
and aircraft. China and some fellow SCS claimants hold
China violated the Philippines’ sovereign rights by
that UNCLOS allows them to regulate both economic
interfering with Philippine vessels, damaging the maritime
activity and foreign militaries’ navigation and overflight
environment, and engaging in reclamation work on a
through their EEZs.
feature in the Philippines’ EEZ. The United States has
urged China and the Philippines to abide by the ruling,
In recent years, the U.S. Navy and Air Force have stepped
which under UNCLOS is binding on both parties. China,
up the pace and public profile of their activities in the South
however, declared the ruling “null and void.” China and the
China Sea. The U.S. Navy conducts Freedom of Navigation
10-member Association of Southeast Asian Nations
Operations (FONOPs), challenging maritime claims that the
(ASEAN) are negotiating a Code of Conduct (COC) for
United States considers to be excessive. It also seeks to
parties in the SCS. Many observers believe that a binding
maintain an ongoing presence in the SCS “to uphold a free
COC is unlikely, and that China has prolonged the
and open international order,” while the U.S. Air Force flies
negotiations to buy time to carry out actions aimed at
bomber missions over the SCS. China regularly conducts
further strengthening its position in the SCS.
military patrols and training in the SCS, and objects
strenuously to U.S. military activities there. PRC officials
U.S. Actions
regularly say that U.S. presence operations in the SCS
Several U.S. Administrations have sought to address
undermine regional peace and stability. A PRC Foreign
tensions in the SCS. In 2020, the Commerce Department
Ministry spokesperson said in 2021 that such operations are
added to its Entity List PRC construction, energy, and
“nothing but the ‘freedom of trespassing’ enjoyed by [U.S.
shipbuilding companies involved in the SCS, barring U.S.
military aircraft and ships] in saber-rattling and making
companies from exporting to the firms without a
provocations.”
government license. Biden Administration officials have
regularly stated objections to PRC actions. In August 2022,
China and the other SCS claimants (except Taiwan, which
Secretary of State Antony Blinken told incoming Philippine
is not a member of the United Nations) are parties to
President Ferdinand Marcos Jr. that under the United
UNCLOS. The United States is not a party, but has long
States-Philippines Mutual Defense Treaty, the United States
had a policy of abiding by UNCLOS provisions relating to
would assist Philippine forces in the event of a South China
maritime disputes and rights. UNCLOS allows state parties
Sea contingency. The United States has stepped up security
to claim 12-nm territorial seas and 200-nm EEZs around
cooperation with Japan, Indonesia, Malaysia, the
their coastlines and “naturally formed” land features that
Philippines, Singapore, and Vietnam; undertaken joint
can “sustain human habitation.” Rocks that are above water
patrols in the SCS with other partners, including Japan,
at high tide but not habitable generate only territorial seas.
India, and Australia; and expressed support for other
multilateral actions in the region. The Quadrilateral
China’s Artificial Island Building
Security Dialogue—a grouping of the United States, Japan,
Between 2013 and 2015, China undertook extensive land
Australia, and India—announced in May 2022 an effort to
reclamation in the SCS’ Spratly Island chain. According to
improve maritime domain awareness throughout the Indo-
the U.S. Department of Defense (DOD), the reclamation
Pacific, including the SCS.
created over 3,200 acres (five square miles) of artificial
Select Legislation
landmasses on the seven disputed sites that China controls.
China built military infrastructure on the outposts, and
Under a security assistance program currently known as the
beginning in 2018, deployed advanced anti-ship and anti-
Indo-Pacific Maritime Security Initiative authorized by
aircraft missile systems and military jamming equipment.
Congress in the National Defense Authorization Act
(NDAA) for Fiscal Year (FY) 2016 (P.L. 114-92) and
China portrays its actions as part of an effort to play catch-
modified in the NDAAs for FYs 2017, 2019, 2022, and
up to other claimants, several of which control more
2023, the United States has sought to improve the ability of
Spratlys features and carried out earlier reclamation and
regional countries to enhance maritime domain awareness
construction work on them, although the scale of China’s
(MDA) and patrol their EEZs.
reclamation work and militarization has greatly exceeded
that of other claimants. DOD’s 2022 report on PRC military
The William M. (Mac) Thornberry National Defense
and security developments stated that the Spratly Island
Authorization Act for FY2021 (P.L. 116-283) established a
outposts “allow China to maintain a more flexible and
Pacific Deterrence Initiative to strengthen U.S. defense
persistent military and paramilitary presence in the area,”
posture in the Indo-Pacific region, addressing issues such as
which “improves China’s ability to detect and challenge
those in the SCS. The act included a statement that China’s
“
activities by rival claimants or third parties and widens the
baseless territorial claims,” including in the SCS, “are
destabilizing and inconsistent with international law.”
range of response options available to Beijing.”
Congress extended and expanded the Pacific Deterrence
UNCLOS and the SCS
Initiative in subsequent NDAAs.
In 2013, the Philippines sought arbitration under UNCLOS
over PRC actions in the SCS. In July 2016, an UNCLOS
Ben Dolven, Specialist in Asian Affairs
arbitral tribunal ruled that China’s nine-dash line claim had
Caitlin Campbell, Analyst in Asian Affairs
“no legal basis.” It also ruled that none of the land features
Ronald O'Rourke, Specialist in Naval Affairs
in the Spratlys is entitled to any more than a 12-nm
IF10607
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China Primer: South China Sea Disputes
Disclaimer
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https://crsreports.congress.gov | IF10607 · VERSION 10 · UPDATED