Updated July 5, 2023
South Korea: Background and U.S. Relations
Overview
North Korea Policy Coordination
South Korea (officially the Republic of Korea, or ROK) is
Historically, North Korea has been the dominant strategic
one of the United States’ most important strategic and
concern in the U.S.-ROK relationship. Whereas the previous
economic partners in Asia. The U.S.-ROK Mutual Defense
ROK government emphasized diplomacy with North Korea,
Treaty, signed in 1953 at the end of the Korean War,
Yoon and Biden have emphasized deterrence. They have
commits the United States to help South Korea defend itself,
reactivated high-level consultations on extended deterrence
particularly from North Korea (officially the Democratic
under the U.S. nuclear umbrella and expanded the scope and
People’s Republic of Korea, or DPRK). Approximately
scale of combined military exercises (including with Japan),
28,500 U.S. troops are based in the ROK. The economic
which President Donald Trump and Yoon’s predecessor had
relationship is bolstered by the U.S.-South Korea Free Trade
curtailed. The United States has increased deployments of
Agreement (KORUS FTA), implemented in 2012. In 2022,
strategic assets—such as nuclear-armed submarines—to
South Korea was the United States’ seventh-largest trading
South Korea, introduced new unilateral sanctions
partner (goods and services trade combined), and the United
designations on North Korea, and proposed new DPRK
States was South Korea’s second-largest trading partner,
sanctions measures in the United Nations. (China and
behind the People’s Republic of China (PRC, or China).
Russia vetoed the attempt.)
Over the past decade, congressional interest in U.S.-ROK
relations often has focused on U.S.-ROK cooperation on
Alongside these steps, the two allies have offered
North Korea, Indo-Pacific policies, the U.S.-ROK alliance,
Pyongyang unconditional humanitarian assistance, and
and U.S.-South Korea trade and investment flows.
Yoon has pledged large-scale economic assistance if North
Korea “embarks on a genuine and substantive process for
South Korean President Yoon Suk-yeol, in office since May
denuclearization.” Biden Administration officials say they
2022, is seeking to transform South Korea into a “global
have reached out to North Korea, offering to meet “without
pivotal state” by raising its profile beyond the Korean
preconditions.” Since the collapse of Trump’s diplomatic
Peninsula and becoming a more active partner in the United
engagement with North Korean leader Kim Jong-un in
States’ Indo-Pacific strategy. Yoon issued South Korea’s
2019, however, Pyongyang largely has ignored U.S. and
first-ever Indo-Pacific strategy in 2022. U.S. President
South Korean outreach. If negotiations restart, the
Joseph Biden and Yoon have capitalized on greater U.S.-
Administration appears to envision offering some sanctions
ROK strategic alignment by forging closer cooperation on
relief in exchange for steps toward denuclearization.
North Korea policy through both bilateral and trilateral
(with Japan) military exercises. They also have committed
Since the start of 2022, North Korea has test-launched more
to strengthening economic security in line with U.S. efforts
than 80 missiles, including multiple tests of intercontinental
to promote technological development and supply chain
ballistic missiles (ICBMs), which are capable of delivering
resiliency. South Korea is one of 14 negotiating partners in
nuclear warheads, and has boosted relations with Russia and
the U.S.-led Indo-Pacific Economic Framework for
China. Analysts are concerned that North Korea may
Prosperity (IPEF) initiative, a proposed new trade and
conduct its seventh nuclear weapons test, which would be
economic arrangement.
the first since September 2017. In 2022, Kim pledged to
“exponentially increase” North Korea’s nuclear weapons
The increased U.S.-ROK alignment was on display in April
stockpile, said he will “never” denuclearize, and
2023, when Biden hosted Yoon for a State Visit. During his
promulgated a law expanding the conditions under which
visit, Yoon became the 7th ROK president to address a Joint
North Korea would use nuclear weapons to include non-
Meeting of Congress, and the first to do so since 2013.
nuclear attacks and situations that threaten the regime’s
Biden and Yoon issued a broad joint statement proclaiming
survival. Pyongyang continues to evade sanctions and
a “global comprehensive strategic alliance.” To address
conduct illicit activities to raise funds.
increased South Korean concerns about the credibility of the
U.S. commitment to ROK security, they also issued “the
U.S.-South Korea Security Issues
Washington Declaration” on extended deterrence. In the
The Biden Administration has worked to repair and expand
document, the United States agrees to expand consultations
the alliance, which had been strained under Trump,
with South Korea on the use of U.S. nuclear weapons on the
prompting the 115th and 116th Congresses to impose
Korean Peninsula and to “enhance the regular visibility of
conditions (via National Defense Authorization Acts) on the
strategic assets,” including nuclear-capable weapons
President’s power to withdraw U.S. troops from South
systems, deployed to the Peninsula. South Korea restated its
Korea. In 2021, the Biden Administration concluded a cost-
commitment not to develop nuclear weapons. Since the late
sharing negotiation with South Korea—an earlier agreement
2010s, as North Korea has advanced its nuclear and missile
had expired in 2019—that boosted South Korea’s
capabilities, opinion polls have shown strong support from
contribution to alliance costs by 13.9%. The ROK
the ROK public to build independent nuclear weapons.
traditionally has paid for about 50% (over $800 million
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South Korea: Background and U.S. Relations
annually) of the total non-personnel costs of the U.S.
nonlethal equipment. Poland has signed contracts to
military presence. U.S. forces in South Korea also have
purchase over $3 billion in South Korean arms to replace
consolidated their bases, in part to return land to the ROK.
equipment sent to assist Ukraine, and in the spring of 2023
South Korea has paid $9.7 billion—about 94% of total
South Korea reportedly began transferring hundreds of
costs—to construct new facilities such as Camp Humphreys,
thousands of artillery rounds to the United States, which
the largest overseas U.S. base.
planned to send them to Ukraine.
Washington and Seoul have adapted the alliance to
U.S.-South Korea Economic Relations
recognize South Korea’s increased military capabilities and
U.S. goods and services exports to South Korea totaled
desire for greater autonomy. Since 2006, they have been
$95.5 billion in 2022, and imports totaled $132.0 billion.
preparing to transfer wartime operational control (OPCON)
Autos and auto parts accounted for one-quarter of U.S.
to a binational command led by an ROK general with a U.S.
imports ($33.6 billion). In 2021, the stock of South Korean
deputy. Currently, ROK forces would be under a binational
FDI in the United States was $72.5 billion, up 14.9% from
command led by a U.S. general in wartime. The two sides
2020, and U.S. FDI to South Korea was $38.1 billion. Over
have established conditions and benchmarks to demonstrate
80,000 workers in the United States were employed by
that the ROK can assume wartime OPCON, including
ROK multinational firms in 2020. In 2022, ROK companies
improved ROK capabilities and a conducive security
pledged $25 billion in new investment in key industries
environment on the Peninsula. In 2021 the allies terminated
including electric vehicles (EVs), semiconductors, and
a 1979 agreement that limited the range of ROK ballistic
biotechnology.
missiles to 800 kilometers (497 miles).
The KORUS FTA has been the centerpiece of U.S.-South
South Korea’s Regional Relations
Korea trade and investment relations since its entry into
For years, China has been South Korea’s largest trading
force in 2012. Most U.S. business groups support the
partner and second-largest destination for foreign direct
agreement, highlighting market access improvements in
investment (FDI). In the past, Beijing has imposed
South Korea and a more robust mechanism for dispute
retaliatory economic measures on South Korean companies
resolution. The Trump Administration negotiated limited
for Seoul’s foreign policy choices. South Korean opinion
modifications to the KORUS FTA, which took effect in
polls show strong negative attitudes toward China. Even as
2019, to address some implementation concerns. South
Yoon has shown caution in his relations with China, he has
Korea’s participation in the IPEF initiative may provide an
pushed back against PRC criticism of the ROK’s expansion
opportunity to further enhance economic ties, including on
of its military posture and its security cooperation with the
digital trade issues, a priority area for both countries.
United States and Japan. He also has indicated interest in
South Korea had raised concerns over tax credit and federal
joining the vaccine, climate change, and emerging
funding requirements in P.L. 117-169, commonly called the
technology working groups established by the Quadrilateral
Inflation Reduction Act, and P.L. 117-167, commonly
Security Dialogue (or “Quad”), a group comprising
called the CHIPS and Science Act, for EVs and
Australia, India, Japan, and the United States that PRC
semiconductor-related activities. The South Korean
officials criticized as a U.S.-led “anti-China alliance.” PRC
government has stated that it will continue working with the
officials reportedly have said if ROK policy trends continue,
United States to address these concerns. Trump-era import
Beijing will curtail cooperation with Seoul on North Korea.
restrictions on ROK steel, aluminum, and solar products
ROK-Japan relations are perennially fraught because of
remain in effect.
sensitive legacy issues from Japan’s colonization of the
Korean Peninsula from 1910 to 1945. In 2018 and 2019, a
South Korean Politics
series of actions and retaliatory countermeasures by both
Yoon, who won election by a margin of less than 1%, is
governments involving trade, security, and history-related
contending with a National Assembly firmly controlled by
controversies caused relations to plummet, eroding U.S.-
the opposition Minjoo Party (see Figure 1) and with public
ROK-Japan policy coordination. With encouragement from
approval ratings generally below 40%. These factors limit
the Biden Administration, Tokyo and Seoul took steps to
Yoon’s flexibility in implementing his policy choices.
reverse this trend in 2022 and 2023, including three bilateral
heads-of-state meetings (the first since 2019), multiple
Figure 1. South Korea’s National Assembly
ROK-Japan-U.S. summits, expanded trilateral military
exercises, and an agreement to share data on DPRK missiles
in real time. In March 2023, the Yoon government removed
a major source of friction by arranging for an ROK
foundation to compensate the families of South Koreans
forced to work by Japanese companies during the colonial
period, instead of insisting the companies pay the victims,
as the ROK Supreme Court had ruled. Although relations
Source: National Assembly website, accessed April 5, 2023.
have markedly improved, distrust over historical issues
remains a source of tension between the two U.S. allies.
Mark E. Manyin, Specialist in Asian Affairs
Since Russia’s February 2022 invasion of Ukraine, South
Emma Chanlett-Avery, Specialist in Asian Affairs
Korea has imposed sanctions against Russia and provided
Liana Wong, Analyst in International Trade and Finance
Ukraine with over $200 million in humanitarian aid and
IF10165
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South Korea: Background and U.S. Relations
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https://crsreports.congress.gov | IF10165 · VERSION 42 · UPDATED