Updated April 6, 2023
South Korea: Background and U.S. Relations
Overview
Administration appears to envision offering some sanctions
South Korea (officially the Republic of Korea, or ROK) is
relief in exchange for steps toward denuclearization.
one of the United States’ most important strategic and
Administration officials say they have reached out to North
economic partners in Asia. The U.S.-ROK Mutual Defense
Korea, offering to meet “without preconditions,” and that
Treaty, signed in 1953 at the end of the Korean War,
“the ball is in [Pyongyang’s] court.” Since the collapse of
commits the United States to help South Korea defend
former President Donald Trump’s meetings with North
itself, particularly from North Korea (officially the
Korean leader Kim Jong-un in 2019, however, Pyongyang
Democratic People’s Republic of Korea, or DPRK).
largely has ignored U.S. and South Korean outreach.
Approximately 28,500 U.S. troops are based in the ROK.
The economic relationship is bolstered by the U.S.-South
Since the start of 2022, North Korea has test-launched more
Korea Free Trade Agreement (KORUS FTA), implemented
than 60 missiles, including multiple tests of intercontinental
in 2012. In 2022, South Korea was the United States’
ballistic missiles (ICBMs), which are capable of delivering
seventh-largest trading partner (goods and services trade
nuclear warheads. Satellite imagery publicized in 2022
combined), and the United States was South Korea’s
appeared to indicate repairs and enhancements at North
second-largest trading partner, behind the People’s
Korea’s nuclear weapons test site, raising concerns that it
Republic of China (PRC, or China). Over the past decade,
will conduct its seventh nuclear weapons test, which would
congressional interest in U.S.-ROK relations often has
be the first since September 2017. In 2022, Kim pledged to
focused on U.S.-ROK cooperation over North Korea and
“exponentially increase” North Korea’s nuclear weapons
more recently Indo-Pacific policies, the U.S.-ROK alliance,
stockpile, said he will “never” denuclearize, and
and U.S.-South Korea trade and investment flows.
promulgated a new law expanding the conditions under
which North Korea would use nuclear weapons to include
South Korean President Yoon Suk-yeol, in office since May
non-nuclear attacks and situations that threaten the regime’s
2022, is seeking to transform South Korea into a “global
survival. Pyongyang continues to evade sanctions and
pivotal state” by raising its profile beyond the Korean
conduct illicit activities to raise funds. Inter-Korean
Peninsula and becoming a more active partner in the United
tensions have increased since Yoon, who has taken a harder
States’ Indo-Pacific strategy. Yoon issued South Korea’s
line on North Korea than his predecessor, took office.
first-ever Indo-Pacific strategy in 2022. President Joseph
Biden and Yoon have capitalized on greater U.S.-ROK
Whereas the previous ROK government emphasized
strategic alignment by forging closer cooperation on North
diplomacy with North Korea, Yoon and Biden have
Korea policy through military exercises and expanding
emphasized deterrence. They have reactivated high-level
trilateral cooperation with Japan. They also have made
consultations on extended deterrence under the U.S. nuclear
efforts to integrate South Korean companies with U.S.
umbrella and expanded the scope and scale of combined
efforts to promote technological development and supply
military exercises (including with Japan), which President
chain resiliency. South Korea is one of 14 negotiating
Trump and Yoon’s predecessor, Moon Jae-in, had curtailed
partners in the U.S.-led Indo-Pacific Economic Framework
since 2018. The United States has increased deployments of
for Prosperity (IPEF) initiative, a proposed new trade and
strategic assets such as stealth fighter jets, introduced new
economic arrangement. Despite the growing alignment,
unilateral sanctions designations, and proposed new DPRK
South Korea’s approach to China is less confrontational
sanctions measures in the United Nations. (China and
than the United States’, and U.S.-ROK economic friction
Russia vetoed the attempt.) Alongside these steps, the two
had increased due to South Korean complaints about the
allies have offered Pyongyang unconditional humanitarian
electronic vehicle (EV) provisions in P.L. 117-169, known
assistance, and Yoon has pledged to provide large-scale
as the Inflation Reduction Act of 2022 (IRA). On April 26,
economic assistance if North Korea “embarks on a genuine
2023, Biden is scheduled to host Yoon Suk-yeol for a State
and substantive process for denuclearization.”
Visit, including a state dinner, to celebrate the 70th
anniversary of the U.S.-ROK alliance. Yoon has been
U.S.-South Korea Security Issues
invited to address a Joint Meeting of Congress on April 27.
The Biden Administration has worked to repair the alliance,
which had been strained under Trump, prompting the 115th
North Korea Policy Coordination
and 116th Congresses to impose conditions (via the
Historically, North Korea has been the dominant strategic
FY2019, FY2020, and FY2021 National Defense
concern in the U.S.-ROK relationship. The Biden
Authorization Acts) on the President’s power to withdraw
Administration in 2021 stated it will pursue an “approach
U.S. troops from South Korea. In February 2021, the Biden
that is open to and will explore diplomacy with North
Administration concluded a cost-sharing negotiation with
Korea” to eventually achieve the “complete
South Korea that boosted South Korea’s contribution to
denuclearization of the Korean Peninsula,” even as U.S.
alliance costs by 13.9%. The ROK traditionally has paid for
and international sanctions remain in place. The
about 50% (over $800 million annually) of the total non-
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South Korea: Background and U.S. Relations
personnel costs of the U.S. military presence, according to
trilateral military exercises, and an agreement to share data
congressional testimony by U.S. military officials.
on DPRK missiles in real time. In March 2023, the Yoon
government removed a major source of friction by
Washington and Seoul have been adapting the alliance to
arranging for an ROK foundation to compensate South
recognize South Korea’s increased military capabilities and
Koreans forced to work by Japanese companies during the
desire for greater autonomy. For over a decade, they have
colonial period, instead of insisting the companies pay the
been preparing to transfer wartime operational control
victims, as the ROK Supreme Court had ruled. Although
(OPCON) to a binational command led by an ROK general
relations have improved, distrust over historical issues
with a U.S. deputy. Under the existing arrangement, South
remains a source of tension between the two U.S. allies.
Korean forces would be under a binational command led by
a U.S. general in the event of war. The two sides have
U.S.-South Korea Economic Relations
established conditions and benchmarks to demonstrate that
U.S. goods and services exports to South Korea totaled
the ROK can assume wartime OPCON, including improved
$95.5 billion in 2022, and imports totaled $132.0 billion.
ROK capabilities to lead combined forces and counter the
Autos and parts accounted for one-quarter of U.S. imports
DPRK nuclear and missile threat, and a security
($33.6 billion). In 2021, the stock of South Korean FDI in
environment on the Peninsula conducive to a transfer.
the United States was $72.5 billion, up 14.9% from 2020,
Additionally, U.S. forces in the ROK have consolidated
and U.S. FDI to South Korea was $38.1 billion. Over
their presence, in part to return land to South Korea. South
80,000 workers in the United States were employed by
Korea has paid $9.7 billion—about 94% of total costs—to
South Korean multinational firms in 2020. In 2022, South
construct new facilities such as Camp Humphreys, the
Korean companies pledged $25 billion in new investment in
largest overseas U.S. base. Another example of alliance
key industries including EVs, semiconductors, and
adaptation is a 2021 decision to terminate the 1979 bilateral
biotechnology.
Missile Guidelines agreement, which limited the range of
The KORUS FTA has been the centerpiece of U.S.-South
ROK ballistic missiles to 800 kilometers (497 miles).
Korea trade and investment relations since its entry into
Reaction to Russia’s War in Ukraine
force in 2012. Most U.S. business groups support the
Since Russia’s February 2022 invasion of Ukraine, South
agreement, highlighting market access improvements in
Korea has imposed sanctions against Russia and offered
South Korea and a more robust mechanism for dispute
over $200 million in humanitarian aid and nonlethal
resolution. The Trump Administration negotiated limited
equipment to Ukraine. Poland has signed contracts to
modifications to the KORUS FTA, which took effect in
purchase over $3 billion in South Korean arms to replace
2019, to address some implementation concerns. The two
equipment sent to assist Ukraine. Yoon also joined a 2022
countries continue to engage on outstanding issues. South
NATO summit in Madrid, a first for an ROK leader.
Korea’s participation in the IPEF initiative may provide an
opportunity to further enhance economic ties, including on
South Korea’s Regional Relations
digital trade issues, a priority area for both countries.
China is South Korea’s largest trading partner and second-
South Korea had raised concerns over the IRA’s assembly
largest destination for foreign direct investment (FDI). In
and sourcing requirements, and engaged in bilateral
the past, Beijing has imposed retaliatory economic
measures on South Korean companies for Seoul’s policy
discussions with the Biden Administration as the Treasury
Department wrote implementing rules. The Yoon
choices. Also, PRC support or opposition could be decisive
in shaping the outcome of South Korea’s
government reacted positively to the new rules published on
DPRK policies.
March 31, 2023. Trump-era import restrictions on ROK
Opinion polls show strong negative South Korean attitudes
steel, aluminum, solar, and other products, remain in effect.
toward China. Even as Yoon often has shown caution in his
relations with China, he has pushed back against China’s
South Korean Politics
efforts to curtail the ROK’s expansion of its military
Yoon, who won the 2022 election by a margin of less than
posture and its security cooperation with the United States
1%, is contending with a National Assembly firmly
and Japan. He also has indicated interest in participating in
controlled by the opposition Minjoo Party (see Figure 1)
the vaccine, climate change, and emerging technology
and with public approval ratings generally below 40%.
working groups established by the Quadrilateral Security
Dialogue (or “Quad”), a group comprising Australia, India,
Figure 1. South Korea’s National Assembly
Japan, and the United States that PRC officials have
criticized as being part of a U.S.-led “anti-China alliance.”
ROK-Japan relations are perennially fraught because of
sensitive legacy issues from Japan’s colonization of the
Korean Peninsula from 1910 to 1945. In 2018 and 2019, a
series of actions and retaliatory countermeasures by both
governments involving trade, security, and history-related
controversies caused South Korea-Japan relations to
Source: National Assembly website, accessed June 4, 2022.
plummet, eroding U.S.-ROK-Japan policy coordination.
With encouragement from the Biden Administration, Tokyo
Mark E. Manyin, Specialist in Asian Affairs
and Seoul took steps to reverse this trend in 2022 and 2023,
Emma Chanlett-Avery, Specialist in Asian Affairs
including two bilateral heads-of-state meeting (the first
Liana Wong, Analyst in International Trade and Finance
since 2019), multiple ROK-Japan-U.S. summits, expanded
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South Korea: Background and U.S. Relations
IF10165
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