Updated February 2, 2021
South China Sea Disputes: Background and U.S. Policy
Overview
Key Facts
Multiple Asian governments assert sovereignty over rocks,
The SCS is one of the world’s most heavily trafficked
reefs, and other geographic features in the heavily
waterways. An estimated $3.4 trillion in ship-borne
trafficked South China Sea (SCS), with the People’s
commerce transits the sea each year, including energy
Republic of China (PRC or China) arguably making the
supplies to U.S. treaty allies Japan and South Korea.
most assertive claims. The United States makes no
According to the U.S. Energy Information Administration,
territorial claim in the SCS and takes no position on
the SCS contains about 11 billion barrels of oil rated as
sovereignty over any of the geographic features in the SCS,
proved or probable reserves—a level similar to the amount
but has urged that disputes be settled without coercion and
of proved oil reserves in Mexico—and 190 trillion cubic
on the basis of international law. Separate from the
feet of natural gas. The SCS also contains significant fish
sovereignty disputes, the United States and China disagree
stocks, coral, and other undersea resources.
over what rights international law grants foreign militaries
to fly, sail, and operate in a country’s territorial sea or
The Sovereignty Disputes
Exclusive Economic Zone (EEZ).
China asserts “indisputable sovereignty over the islands in
the South China Sea and the adjacent waters” without
Since 2013, the sovereignty disputes and the U.S.-China
defining the scope of its “adjacent waters” claim. On maps,
dispute over freedom of the seas for military ships and
China depicts its claims with a “nine-dash line” that, if
aircraft have converged in the controversy over military
connected, would enclose an area covering approximately
outposts China has built on disputed features in the SCS.
62% of the sea, according to the U.S. Department of State.
U.S. officials saw the outposts as part of a possible Chinese
(The estimate is based on a definition of the SCS’s
effort to dominate the SCS, with the goal of making China a
geographic limits that includes the Taiwan Strait, the Gulf
regional hegemon that can set the rules by which other
of Tonkin, and the Natuna Sea.) China has never explained
regional actors must operate. A longstanding goal of U.S.
definitively what the dashed line signifies. In the northern
strategy has been to prevent the emergence of such a
part of the sea, China, Taiwan, and Vietnam contest
regional hegemon. At his January 2021 confirmation
sovereignty of the Paracel Islands; China has occupied them
hearing, Secretary of Defense Lloyd Austin asserted that
since 1974. In the southern part of the sea, China, Taiwan,
China is “already a regional hegemon” and seeks to become
and Vietnam claim all of the approximately 200 Spratly
“a dominant world power.” Observers have been alert to
Islands, while Brunei, Malaysia, and the Philippines, a U.S.
other actions China might take to dominate the SCS,
treaty ally, claim some of them. Vietnam controls the
including initiating reclamation on another SCS geographic
greatest number. In the eastern part of the sea, China,
feature, such as Scarborough Shoal, or declaring an Air
Taiwan, and the Philippines all claim Scarborough Shoal;
Defense Identification Zone (ADIZ) over parts of the SCS.
China has controlled it since 2012. China’s “nine-dash line”
and Taiwan’s similar “eleven-dash line” overlap with the
Figure 1. The South China Sea
theoretical 200-nautical-mile (nm) EEZs that five Southeast
Asian nations—Brunei, Indonesia, Malaysia, the
Philippines, and Vietnam—could claim from their mainland
coasts under the 1994 United Nations Convention on the
Law of the Sea (UNCLOS). Indonesia also disputes China’s
assertions of maritime rights near its coast.
Dispute over Freedom of the Seas
A dispute over how to interpret UNCLOS lies at the heart
of tensions between China and the United States over the
activities of U.S. military vessels and planes in and over the
South China Sea and other waters off China’s coast. The
United States and most other countries interpret UNCLOS
as giving coastal states the right to regulate economic
activities within their EEZs, but not the right to regulate
navigation and overflight through the EEZ, including by
military ships and aircraft. China and some fellow SCS
claimants hold that UNCLOS allows them to regulate both
economic activity and foreign militaries’ navigation and
overflight through their EEZs.

Source: CRS graphic.
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South China Sea Disputes: Background and U.S. Policy
In recent years, the U.S. Navy and Air Force have stepped
tribunal’s ruling, has not sought to enforce it. China and the
up the pace and public profile of their activities in the South
10-member Association of Southeast Asian Nations
China Sea. The U.S. Navy conducts Freedom of Navigation
(ASEAN) are negotiating a Code of Conduct for parties in
Operations (FONOPs), challenging maritime claims that the
the SCS, although many observers believe that a mutually
United States considers to be excessive. It also seeks to
acceptable Code will be difficult to conclude.
maintain an ongoing presence in the SCS “to uphold a free
U.S. Actions
and open international order,” while the U.S. Air Force flies
bomber missions over the SCS. China regularly conducts
Several U.S. Administrations have sought to address
military patrols and training in the SCS, and objects
tensions in the SCS. In 2020, the Commerce Department
strenuously to U.S. military activities there. In response to
added to its Entity List Chinese construction, energy, and
U.S. FONOPs in 2020, China twice accused the United
shipbuilding companies involved in the SCS, barring U.S.
States of “trespassing” in its territorial waters and
companies from exporting to the firms without a
demanded that the United States “strictly control” its SCS
government license. In January 2021, Secretary of State
military activities in order to avoid “unexpected incidents.”
Antony J. Blinken told his Philippine counterpart that the
U.S.-Philippines Mutual Defense Treaty applies to “armed
China and the other SCS claimants (except Taiwan, which
attacks against the Philippine armed forces, public vessels,
is not a member of the United Nations) are parties to
or aircraft in the Pacific, which includes the South China
Sea.” Blinken also
UNCLOS. The United States is not a party, but has long
stated that the United States rejects PRC
had a policy of abiding by UNCLOS provisions relating to
maritime claims in the SCS that exceed maritime zones
maritime disputes and rights. UNCLOS allows state parties
permitted under UNCLOS, and committed “to stand with
Southeast Asian claimants in the face of PRC pressure.”
to claim 12-nm territorial seas and 200-nm EEZs around

their coastlines and “naturally formed” land features that
Under a DOD Indo-Pacific Maritime Security Initiative
can “sustain human habitation.” Rocks that are above water
originally announced in 2015 and broadened in 2019, the
at high tide but not habitable generate only territorial seas.
United States has sought to improve the ability of the
China’s Artificial Island Building
Philippines, Vietnam, and other Southeast Asian countries
to maintain maritime domain awareness (MDA) and patrol
Between 2013 and 2015, China undertook extensive land
their EEZs. The United States has stepped up security
reclamation in the SCS’ Spratly Island chain. According to
cooperation with Japan, Indonesia, Malaysia, the
the U.S. Department of Defense (DOD), the reclamation
Philippines, Singapore, and Vietnam; undertaken joint
created over 3,200 acres (five square miles) of artificial
patrols in the SCS with other partners, including Japan,
landmasses on the seven disputed sites that China controls.
India, and Australia; and expressed support for other
China built military infrastructure on the outposts, and
multilateral actions in the region.
beginning in early 2018, deployed advanced anti-ship and
anti-aircraft missile systems and military jamming
Select Legislation in the 116th Congress
equipment. China portrays its actions as part of an effort to
The National Defense Authorization Act (NDAA) for
play catch-up to other claimants, several of which control
FY2021 (P.L. 116-283) establishes a Pacific Deterrence
more Spratlys features and carried out earlier reclamation
Initiative to strengthen U.S. defense posture in the Indo-
and construction work on them, although the scale of
Pacific region, addressing issues such as those in the SCS.
China’s reclamation work and militarization has exceeded
The act includes a statement that China’s “baseless
that of other claimants. DOD’s 2020 report on PRC military
territorial claims,” including in the SCS, “are destabilizing
and security developments stated that the Spratly Island
and inconsistent with international law.” The NDAA for
outposts “allow China to maintain a more flexible and
FY2020 (P.L. 116-92) states that it is U.S. policy that an
persistent military and paramilitary presence in the area,”
armed attack on Philippine armed forces, vessels or aircraft,
which “improves China’s ability to detect and challenge
including in the SCS, would trigger mutual defense
activities by rival claimants or third parties and widens the
obligations under the U.S.-Philippines defense treaty. The
range of response options available to China.”
act also requires that the annual DOD report on PRC
military and security developments discuss the implications
UNCLOS and the SCS
of a change in the China Coast Guard’s command structure
In 2013, the Philippines sought arbitration under UNCLOS
for PRC “gray zone” activities in the East China Sea and
over Chinese behavior in the SCS. In July 2016, an
SCS. The Consolidated Appropriations Act, 2021 (P.L.
UNCLOS arbitral tribunal ruled that China’s nine-dash line
116-260) conditions assistance for Cambodia on State
claim had “no legal basis.” It also ruled that none of the
Department certification that the country is taking effective
land features in the Spratlys is entitled to any more than a
steps to strengthen regional security, “particularly regarding
12-nm territorial sea; three of the Spratlys features that
territorial disputes in the [SCS].” The act also directs the
China occupies generate no entitlement to maritime zones;
National Geospatial-Intelligence Agency to undertake and
and China violated the Philippines’ sovereign rights by
make public unclassified analysis of PRC activities,
interfering with Philippine vessels, damaging the maritime
including PRC land reclamation in the SCS.
environment, and engaging in reclamation work on a
feature in the Philippines’ EEZ. The United States has
Ben Dolven, Specialist in Asian Affairs
urged China and the Philippines to abide by the ruling,
Susan V. Lawrence, Specialist in Asian Affairs
which under UNCLOS is binding on both parties. China,
Ronald O'Rourke, Specialist in Naval Affairs
however, declared the ruling “null and void.” Philippine
President Rodrigo Duterte, who took office just before the
IF10607
https://crsreports.congress.gov

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South China Sea Disputes: Background and U.S. Policy


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https://crsreports.congress.gov | IF10607 · VERSION 6 · UPDATED

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