Updated December 22, 2020
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 SCS 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 has no territorial
According to the U.S. Energy Information Administration,
claim in the SCS and does not take a 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 right to fly, sail, and operate in a country’s territorial sea
The Sovereignty Disputes
or 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. Of
62% of the sea, according to the U.S. Department of State.
particular concern to the U.S. military is the possibility that
China has never explained definitively what the line
the outposts may be part of a Chinese effort to dominate the
signifies. In the northern part of the sea, China, Taiwan, and
South China Sea, with the ultimate goal of making China a
Vietnam contest sovereignty of the Paracel Islands; China
regional hegemon that can set the rules by which other
has occupied them since 1974. In the southern part of the
regional actors must operate. A long-standing goal of U.S.
sea, China, Taiwan, and Vietnam claim all of the
strategy has been to prevent the emergence of such a
approximately 200 Spratly Islands, while Brunei, Malaysia,
regional hegemon. U.S. and regional observers have been
and the Philippines, a U.S. treaty ally, claim some of them.
alert to other actions China might take to achieve
Vietnam controls the greatest number of Spratly features. In
dominance in the SCS, including initiating reclamation on
the eastern part of the sea, China, Taiwan, and the
another SCS geographic feature, such as Scarborough
Philippines all claim Scarborough Shoal; China has
Shoal, or declaring an Air Defense Identification Zone
controlled it since 2012. China’s “nine-dash line” and
(ADIZ) over parts of the SCS.
Taiwan’s similar “eleven-dash line” overlap with the
theoretical 200-nautical-mile (nm) EEZs that five Southeast
Figure 1. The South China Sea
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). In addition, Indonesia 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.

In recent years, the U.S. Navy and Air Force have stepped
Source: CRS graphic
up the pace and public profile of their activities in the South
China Sea. The U.S. Navy conducts Freedom of Navigation
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South China Sea Disputes: Background and U.S. Policy
Operation (FONOPs), challenging maritime claims that the
(ASEAN) are negotiating a separate Code of Conduct for
United States considers to be excessive. It also seeks to
parties in the SCS, although many observers believe that a
maintain an ongoing presence in the SCS “to uphold a free
mutually acceptable Code will be difficult to conclude.
and open international order that promotes security and
prosperity,” while the U.S. Air Force periodically flies
U.S. Actions
bombers over the SCS. China, which regularly conducts
Several U.S. Administrations have sought to address
military patrols and training in the SCS, objects strenuously
tensions in the SCS. In July 2020, the Trump
to such U.S. military activities. In response to U.S.
Administration’s State Department issued a statement
FONOPs in 2020, China twice accused the United States of
calling many of China’s claims and behavior in the SCS
“trespassing” in its territorial waters and demanded that the
“completely unlawful” and stating that “America stands
United States “strictly control” its SCS military activities in
with our Southeast Asian allies and partners in protecting
order to avoid “unexpected incidents.”
their sovereign rights to offshore resources.” In August and
December 2020, the Commerce Department added to its
China and the other SCS claimants (except Taiwan, which
Entity List Chinese construction, energy, and shipbuilding
is not a member of the United Nations) are parties to
companies involved in the SCS, barring U.S. companies
UNCLOS. The United States is not, but has long had a
from exporting to the firms without a government license.
policy of abiding by UNCLOS provisions relating to
maritime disputes and rights. UNCLOS allows state parties
Under a DOD Indo-Pacific Maritime Security Initiative
to claim 12-nm territorial seas and 200-nm EEZs around
originally announced in 2015 and broadened in 2019, the
their coastlines and “naturally formed” land features that
United States has sought to improve the ability of the
can “sustain human habitation.” Rocks that are above water
Philippines, Vietnam, and other Southeast Asian countries
at high tide but not habitable generate only territorial seas.
to maintain maritime domain awareness (MDA) and patrol
their EEZs. The United States has stepped up security
China’s Artificial Island Building
cooperation with Japan, Indonesia, Malaysia, the
Between 2013 and 2015, China undertook extensive land
Philippines, Singapore, and Vietnam; undertaken joint
reclamation in the Spratly Island chain in the SCS.
patrols in the SCS with other partners, including Japan,
According the U.S. Department of Defense (DOD), China’s
India, and Australia; and expressed support for other
reclamation created over 3,200 acres (five square miles) of
multilateral actions in the region.
artificial landmasses on the seven disputed sites that China
controls. China built military infrastructure on the outposts,
Select Legislation in the 116th Congress
and beginning in early 2018, deployed advanced anti-ship
In the 116th Congress, the National Defense Authorization
and anti-aircraft missile systems and military jamming
Act (NDAA) for FY2021 (H.R. 6395) would establish a
equipment. China portrays its actions as part of an effort to
Pacific Deterrence Initiative to strengthen U.S. defense
play catch-up to other claimants, several of which control
posture in the Indo-Pacific Region, addressing issues such
more Spratlys features and carried out earlier reclamation
as those in the SCS. It would also include a sense of
and construction work on them, although China’s
Congress statement that China’s “baseless territorial
reclamation work and militarization have exceeded that of
claims,” including in the SCS, “are destabilizing and
other claimants. DOD’s 2020 report on PRC military and
inconsistent with international law.” The NDAA for
security developments stated that the Spratly Island
FY2020 (P.L. 116-92) states that it is U.S. policy that an
outposts “allow China to maintain a more flexible and
armed attack on Philippine armed forces, vessels or aircraft,
persistent military and paramilitary presence in the area,”
including in the South China Sea, would trigger mutual
which “improves China’s ability to detect and challenge
defense obligations under the U.S.-Philippines defense
activities by rival claimants or third parties and widens the
treaty. It also requires that the annual DOD report to
range of response options available to China.”
Congress on PRC military developments discuss the
implications of a change in the China Coast Guard’s
UNCLOS and the SCS
command structure for PRC “gray zone” activities in the
In 2013, the Philippines sought arbitration under UNCLOS
East China Sea and SCS.
over Chinese behavior in the SCS. In July 2016, an
UNCLOS arbitral tribunal ruled that China’s nine-dash line
The Consolidated Appropriations Act, 2021 (H.R. 133)
claim had “no legal basis.” It also ruled that none of the
would condition assistance for Cambodia on a State
land features in the Spratlys is entitled to any more than a
Department certification that Cambodia is taking effective
12-nm territorial sea; three of the Spratlys features that
steps to “strengthen regional security and stability,
China occupies generate no entitlement to maritime zones;
particularly regarding territorial disputes in the [SCS].” It
and China violated the Philippines’ sovereign rights by
would also require the National Geospatial-Intelligence
interfering with Philippine vessels, damaging the maritime
Agency to undertake and make public unclassified analysis
environment, and engaging in reclamation work on a
of PRC activities, including “[m]aritime land reclamation
feature in the Philippines’ EEZ. The United States has
activities conducted by China in the [SCS].”
urged China and the Philippines to abide by the ruling,
which under UNCLOS is binding on both parties. China,
Ben Dolven, Specialist in Asian Affairs
however, declared the ruling “null and void.” Philippine
Susan V. Lawrence, Specialist in Asian Affairs
President Rodrigo Duterte, who took office just before the
tribunal’s ruling, has
Ronald O'Rourke, Specialist in Naval Affairs
not sought to enforce it. China and the
10-member Association of Southeast Asian Nations
IF10607
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South China Sea Disputes: Background and U.S. Policy


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https://crsreports.congress.gov | IF10607 · VERSION 3 · UPDATED

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