Updated June 25, 2024
South Korea: Background and U.S. Relations
Overview
ROK government emphasized diplomacy with North Korea,
South Korea (officially the Republic of Korea, or ROK) is
Yoon and Biden have emphasized deterrence. They have
one of the United States’ most important strategic and
reactivated high-level consultations on extended deterrence
economic partners in Asia. The U.S.-ROK Mutual Defense
under the U.S. nuclear umbrella and expanded the scope and
Treaty, signed in 1953 at the end of the Korean War,
scale of combined military exercises (including with Japan),
commits the United States to help South Korea defend itself,
which President Donald Trump and Yoon’s predecessor had
particularly from North Korea (officially the Democratic
curtailed. The United States has increased deployments of
People’s Republic of Korea, or DPRK). Approximately
strategic assets—such as nuclear-armed submarines—to
28,500 U.S. troops are based in the ROK. The economic
South Korea, introduced new unilateral sanctions
relationship is bolstered by the U.S.-South Korea Free Trade
designations on North Korea, and proposed new DPRK
Agreement (KORUS FTA), implemented in 2012. In 2022,
sanctions measures in the United Nations. (China and
South Korea was the United States’ seventh-largest trading
Russia vetoed the attempt.)
partner (goods and services trade combined), and the United
States was South Korea’s second-largest trading partner,
Alongside these steps, the two allies have offered
behind the People’s Republic of China (PRC, or China).
Pyongyang unconditional humanitarian assistance, and
Over the past decade, congressional interest in U.S.-ROK
Yoon has pledged large-scale economic assistance if North
relations often has focused on U.S.-ROK cooperation on
Korea “embarks on a genuine and substantive process for
North Korea, Indo-Pacific policies, the U.S.-ROK alliance,
denuclearization.” Biden Administration officials say they
and U.S.-South Korea trade and investment flows.
have reached out to North Korea, offering to meet “without
preconditions.” Pyongyang largely has ignored U.S. and
South Korean President Yoon Suk-yeol, in office since May
South Korean outreach. If negotiations restart, the
2022, is seeking to transform South Korea into a “global
Administration appears to envision offering some sanctions
pivotal state” by raising its profile beyond the Korean
relief in exchange for steps toward denuclearization.
Peninsula and becoming a more active U.S. partner in the
Indo-Pacific. U.S. President Joseph Biden and Yoon have
Tensions on the Korean Peninsula have increased since
forged closer cooperation on North Korea policy, including
2021. In the ensuing period, North Korea has test-launched
through bilateral and trilateral (with Japan) military
more than 80 missiles, including multiple tests of
exercises. They also have committed to strengthening
intercontinental ballistic missiles (ICBMs), which are
economic security in line with U.S. efforts to promote
capable of delivering nuclear warheads. Analysts are
technological development and supply chain resiliency.
concerned that North Korea may conduct its seventh nuclear
weapons test, which would be the first since September
The increased U.S.-ROK alignment was on display during
2017. Kim has pledged to “exponentially increase” North
April 2023, when Biden hosted Yoon for a State Visit and
Korea’s nuclear weapons stockpile and said he will “never”
Yoon spoke to a Joint Meeting of Congress. To address
denuclearize. In 2023, North Korea declared that South
increased South Korean concerns about the credibility of the
Korea is a “hostile state” rather than one inhabited by
U.S. commitment to ROK security, Biden and Yoon issued
“fellow countrymen,” and in 2024 warned of possible
“the Washington Declaration” on extended deterrence. In
military actions in the waters surrounding the Korean
the document, the United States agreed to expand
Peninsula. Since 2022, Kim also has boosted relations with
consultations with South Korea on the use of U.S. nuclear
Russia and China, including forging a new strategic
weapons on the Korean Peninsula and to “enhance the
partnership with Moscow that includes a mutual defense
regular visibility of strategic assets,” including nuclear-
pledge in the event either country is attacked. Analysts
capable weapons systems deployed to the Peninsula. South
worry that possible Russian transfers of advanced military
Korea restated its commitment not to develop nuclear
technology, in addition to China’s increased economic and
weapons. Since the late 2010s, as North Korea has advanced
diplomatic support, could boost North Korea’s military
its nuclear and missile capabilities, opinion polls have
capabilities and embolden Kim to conduct aggressive
shown the ROK public supports developing indigenous
diplomatic, military, or other actions.
nuclear weapons. In August 2023, Biden hosted Yoon and
Japanese Prime Minister Kishida Fumio at Camp David, the
U.S.-South Korea Security Issues
three countries’ first-ever standalone summit meeting. The
The Biden Administration has worked to repair and expand
leaders announced a set of unprecedented initiatives for
the alliance, which had been strained under Trump,
trilateral consultation and collaboration.
prompting the 115th and 116th Congresses to impose
conditions (via National Defense Authorization Acts) on the
North Korea Policy Coordination
President’s power to withdraw U.S. troops from South
Historically, North Korea has been the dominant strategic
Korea. In 2021, the Biden Administration concluded a cost-
concern in the U.S.-ROK relationship. Whereas the previous
sharing negotiation with South Korea—an earlier agreement
https://crsreports.congress.gov

---

South Korea: Background and U.S. Relations
had expired in 2019—that boosted South Korea’s
Meanwhile, since 2022, North Korea reportedly has
contribution to alliance costs by 13.9%. The ROK
provided Russia with ammunition and missiles for use in
traditionally has paid for about 50% (over $800 million
Ukraine.
annually) of the total non-personnel costs of the U.S.
military presence. U.S. forces in South Korea also have
U.S.-South Korea Economic Relations
consolidated their bases, in part to return land to the ROK.
U.S. goods and services exports to South Korea totaled
South Korea has paid $9.7 billion—about 94% of total
$91.3 billion in 2023, and imports totaled $132.0 billion. In
costs—to construct new facilities such as Camp Humphreys,
2022, the stock of South Korean FDI in the United States
the largest overseas U.S. base.
was $74.7 billion and U.S. FDI to South Korea was $36.7
billion. Over 88,000 workers in the United States were
Washington and Seoul have adapted the alliance to
employed by ROK multinational firms in 2021. Since 2021,
recognize South Korea’s increased military capabilities and
ROK companies have reportedly announced at least $100
desire for greater autonomy. Since 2006, they have been
billion in new investment in key industries including electric
preparing to transfer wartime operational control (OPCON)
vehicles (EVs), semiconductors, and biotechnology.
to a binational command led by an ROK general with a U.S.
deputy. Currently, ROK forces would be under a binational
The KORUS FTA has been the centerpiece of U.S.-South
command led by a U.S. general in wartime. The two sides
Korea trade and investment relations since its entry into
have established conditions and benchmarks to demonstrate
force in 2012. Most U.S. business groups support the
that the ROK can assume wartime OPCON, including
agreement, highlighting market access improvements in
improved ROK capabilities and a conducive security
South Korea and a more robust mechanism for dispute
environment on the Peninsula.
resolution. The Trump Administration negotiated limited
modifications to the KORUS FTA, which took effect in
South Korea’s Regional Relations
2019, to address some implementation concerns. South
China. For years, China has been South Korea’s largest
Korea’s participation in the U.S.-led, 14-country Indo-
trading partner and second-largest destination for foreign
Pacific Economic Framework for Prosperity (IPEF) may
direct investment (FDI). In the past, Beijing has imposed
provide an opportunity to further enhance economic ties,
retaliatory economic measures on South Korean companies
including on digital trade issues.
for Seoul’s foreign policy choices. South Korean opinion
The Biden and Yoon administrations agreed to strengthen
polls show strong negative attitudes toward China. Even as
the bilateral economic security partnership and have
Yoon has sought to maintain constructive relations with
cooperated in addressing certain issues. Specifically, South
China, he has pushed back against PRC criticism of the
Korean concerns over EV tax credits and federal funding
ROK’s expansion of its military posture and its security
requirements for semiconductor-related activities in the
cooperation with the United States and Japan. Yoon
Inflation Reduction Act (P.L. 117-169) and the CHIPS and
reportedly has called Taiwan a “global issue” and said
Science Act (P.L. 117-167) seemed to have been largely
China is the source of increased cross-Strait tensions. In
resolved. South Korean chipmakers, subject to U.S. export
May 2024, Yoon hosted a China-Japan-South Korea
controls, received an indefinite waiver from the Department
summit, which had not been held since 2019.
of Commerce in October 2023 that allows them to send
Japan. Traditionally, ROK-Japan relations are fraught
certain equipment to their semiconductor facilities in China.
because of sensitive legacy issues from Japan’s colonization
Trump-era import restrictions on ROK steel, aluminum, and
of the Korean Peninsula from 1910 to 1945. In 2018 and
solar products remain in effect.
2019, a series of actions and retaliatory countermeasures by
both governments caused relations to plummet, eroding
South Korean Politics
U.S.-ROK-Japan policy coordination. With encouragement
Yoon was elected in March 2022 by a margin of less than
from the Biden Administration, Seoul and Tokyo reversed
1% and is constitutionally limited to one five-year term. He
this trend in 2022 and 2023. Since March 2023, there have
is contending with a National Assembly firmly controlled
been eight ROK-Japan heads-of-state meetings, multiple
by the opposition Minjoo Party and with public approval
ROK-Japan-U.S. summits, expanded trilateral military
ratings generally well below 40%.
exercises, a new trilateral mechanism to share real time data
on DPRK missiles, and a trilateral “Commitment to
Figure 1. South Korea’s National Assembly
Consult” on regional conflicts and challenges. Although
ROK-Japan relations have markedly improved, distrust
lingers.
Russia and Ukraine. Since Russia’s February 2022 full
invasion, South Korea has sanctioned Russia, provided
humanitarian aid to Ukraine, backfilled U.S. and Polish
weapons stockpiles, and reportedly transferred artillery

rounds to the United States, which then arranged for them to
Source: National Assembly website, accessed June 6, 2024. President
be sent to Ukraine. However, South Korea has been
Yoon belongs to the People Power Party.
reluctant to provide lethal military equipment directly to
Ukraine. The 2024 Russia-DPRK mutual defense treaty
could prompt South Korea to review this policy, a
Mark E. Manyin, Specialist in Asian Affairs
development Vladimir Putin reportedly has said would
Liana Wong, Analyst in International Trade and Finance
cause Russia to react in a way inimical to ROK interests.
https://crsreports.congress.gov

---

South Korea: Background and U.S. Relations

IF10165


Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff to
congressional committees and Members of Congress. It operates solely at the behest of and under the direction of Congress.
Information in a CRS Report should not be relied upon for purposes other than public understanding of information that has
been provided by CRS to Members of Congress in connection with CRS’s institutional role. CRS Reports, as a work of the
United States Government, are not subject to copyright protection in the United States. Any CRS Report may be reproduced
and distributed in its entirety without permission from CRS. However, as a CRS Report may include copyrighted images or
material from a third party, you may need to obtain the permission of the copyright holder if you wish to copy or otherwise
use copyrighted material.

https://crsreports.congress.gov | IF10165 · VERSION 44 · UPDATED

---