Updated December 21, 2023
South Korea: Background and U.S. Relations
Overview
hosted Yoon and Japanese Prime Minister Kishida Fumio at
South Korea (officially the Republic of Korea, or ROK) is
Camp David, the three countries’ first-ever standalone
one of the United States’ most important strategic and
summit meeting, and announced a set of unprecedented
economic partners in Asia. The U.S.-ROK Mutual Defense
initiatives for trilateral consultation and collaboration that
Treaty, signed in 1953 at the end of the Korean War,
U.S. Administrations have sought for years.
commits the United States to help South Korea defend itself,
particularly from North Korea (officially the Democratic
North Korea Policy Coordination
People’s Republic of Korea, or DPRK). Approximately
Historically, North Korea has been the dominant strategic
28,500 U.S. troops are based in the ROK. The economic
concern in the U.S.-ROK relationship. Whereas the previous
relationship is bolstered by the U.S.-South Korea Free Trade
ROK government emphasized diplomacy with North Korea,
Agreement (KORUS FTA), implemented in 2012. In 2022,
Yoon and Biden have emphasized deterrence. They have
South Korea was the United States’ seventh-largest trading
reactivated high-level consultations on extended deterrence
partner (goods and services trade combined), and the United
under the U.S. nuclear umbrella and expanded the scope and
States was South Korea’s second-largest trading partner,
scale of combined military exercises (including with Japan),
behind the People’s Republic of China (PRC, or China).
which President Donald Trump and Yoon’s predecessor had
Over the past decade, congressional interest in U.S.-ROK
curtailed. The United States has increased deployments of
relations often has focused on U.S.-ROK cooperation on
strategic assets—such as nuclear-armed submarines—to
North Korea, Indo-Pacific policies, the U.S.-ROK alliance,
South Korea, introduced new unilateral sanctions
and U.S.-South Korea trade and investment flows.
designations on North Korea, and proposed new DPRK
sanctions measures in the United Nations. (China and
South Korean President Yoon Suk-yeol, in office since May
Russia vetoed the attempt.)
2022, is seeking to transform South Korea into a “global
pivotal state” by raising its profile beyond the Korean
Alongside these steps, the two allies have offered
Peninsula and becoming a more active partner in the United
Pyongyang unconditional humanitarian assistance, and
States’ Indo-Pacific strategy. Yoon issued South Korea’s
Yoon has pledged large-scale economic assistance if North
first-ever Indo-Pacific strategy in 2022. U.S. President
Korea “embarks on a genuine and substantive process for
Joseph Biden and Yoon have capitalized on greater U.S.-
denuclearization.” Biden Administration officials say they
ROK strategic alignment by forging closer cooperation on
have reached out to North Korea, offering to meet “without
North Korea policy, including through bilateral and trilateral
preconditions.” Pyongyang largely has ignored U.S. and
(with Japan) military exercises. They also have committed
South Korean outreach. If negotiations restart, the
to strengthening economic security in line with U.S. efforts
Administration appears to envision offering some sanctions
to promote technological development and supply chain
relief in exchange for steps toward denuclearization.
resiliency. South Korea is one of 14 negotiating partners in
the U.S.-led Indo-Pacific Economic Framework for
Since the start of 2022, North Korea has test-launched more
Prosperity (IPEF) initiative.
than 80 missiles, including multiple tests of intercontinental
ballistic missiles (ICBMs), which are capable of delivering
The increased U.S.-ROK alignment was on display during
nuclear warheads, and has boosted relations with Russia and
2023. In April 2023, Biden hosted Yoon for a State Visit.
China. Analysts are concerned that North Korea may
During his visit, Yoon became the 7th ROK president to
conduct its seventh nuclear weapons test, which would be
address a Joint Meeting of Congress, and the first to do so
the first since September 2017. In 2022, Kim pledged to
since 2013. Biden and Yoon issued a broad joint statement
“exponentially increase” North Korea’s nuclear weapons
proclaiming a “global comprehensive strategic alliance.” To
stockpile, said he will “never” denuclearize, and
address increased South Korean concerns about the
promulgated a law expanding the conditions under which
credibility of the U.S. commitment to ROK security, they
North Korea would use nuclear weapons to include non-
also issued “the Washington Declaration” on extended
nuclear attacks and situations that threaten the regime’s
deterrence. In the document, the United States agrees to
survival. Pyongyang continues to evade sanctions and
expand consultations with South Korea on the use of U.S.
conduct illicit activities to raise funds. In 2023, North
nuclear weapons on the Korean Peninsula and to “enhance
Korea-Russia cooperation expanded, including Pyongyang’s
the regular visibility of strategic assets,” including nuclear-
sales of weapons to Moscow.
capable weapons systems, deployed to the Peninsula. South
Korea restated its commitment not to develop nuclear
U.S.-South Korea Security Issues
weapons. Since the late 2010s, as North Korea has advanced
The Biden Administration has worked to repair and expand
its nuclear and missile capabilities, opinion polls have
the alliance, which had been strained under Trump,
shown strong support from the ROK public to build
prompting the 115th and 116th Congresses to impose
independent nuclear weapons. In August 2023, Biden
conditions (via National Defense Authorization Acts) on the
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South Korea: Background and U.S. Relations
President’s power to withdraw U.S. troops from South
Ukraine over $200 million and has pledged $300 million
Korea. In 2021, the Biden Administration concluded a cost-
more in humanitarian aid and nonlethal equipment. Poland
sharing negotiation with South Korea—an earlier agreement
has signed contracts to purchase over $3 billion in South
had expired in 2019—that boosted South Korea’s
Korean arms to replace equipment sent to assist Ukraine,
contribution to alliance costs by 13.9%. The ROK
and in the spring of 2023 South Korea reportedly began
traditionally has paid for about 50% (over $800 million
transferring hundreds of thousands of artillery rounds to the
annually) of the total non-personnel costs of the U.S.
United States, which reportedly sent them to Ukraine.
military presence. U.S. forces in South Korea also have
consolidated their bases, in part to return land to the ROK.
U.S.-South Korea Economic Relations
South Korea has paid $9.7 billion—about 94% of total
U.S. goods and services exports to South Korea totaled
costs—to construct new facilities such as Camp Humphreys,
$95.5 billion in 2022, and imports totaled $132.0 billion. In
the largest overseas U.S. base.
2022, the stock of South Korean FDI in the United States
was $74.7 billion and U.S. FDI to South Korea was $36.6
Washington and Seoul have adapted the alliance to
billion. Over 88,000 workers in the United States were
recognize South Korea’s increased military capabilities and
employed by ROK multinational firms in 2021. Since 2021,
desire for greater autonomy. Since 2006, they have been
ROK companies have reportedly announced at least $100
preparing to transfer wartime operational control (OPCON)
billion in new investment in key industries including electric
to a binational command led by an ROK general with a U.S.
vehicles (EVs), semiconductors, and biotechnology.
deputy. Currently, ROK forces would be under a binational
command led by a U.S. general in wartime. The two sides
The KORUS FTA has been the centerpiece of U.S.-South
have established conditions and benchmarks to demonstrate
Korea trade and investment relations since its entry into
that the ROK can assume wartime OPCON, including
force in 2012. Most U.S. business groups support the
improved ROK capabilities and a conducive security
agreement, highlighting market access improvements in
environment on the Peninsula.
South Korea and a more robust mechanism for dispute
resolution. The Trump Administration negotiated limited
South Korea’s Regional Relations
modifications to the KORUS FTA, which took effect in
For years, China has been South Korea’s largest trading
2019, to address some implementation concerns. South
partner and second-largest destination for foreign direct
Korea’s participation in the IPEF initiative may provide an
investment (FDI). In the past, Beijing has imposed
opportunity to further enhance economic ties, including on
retaliatory economic measures on South Korean companies
digital trade issues, a priority area for both countries.
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. PRC
resolved. South Korean chipmakers, subject to U.S. export
officials reportedly have said if ROK policy trends continue,
controls, received an indefinite waiver from the Department
Beijing will curtail cooperation with Seoul on North Korea.
of Commerce in October 2023 that allows them to send
Traditionally, ROK-Japan relations are fraught because of
certain equipment to their semiconductor facilities in China.
sensitive legacy issues from Japan’s colonization of the
Trump-era import restrictions on ROK steel, aluminum, and
Korean Peninsula from 1910 to 1945. In 2018 and 2019, a
solar products remain in effect.
series of actions and retaliatory countermeasures by both
governments involving trade, security, and history-related
South Korean Politics
controversies caused relations to plummet, eroding U.S.-
Yoon, who won election by a margin of less than 1%, is
ROK-Japan policy coordination. With encouragement from
contending with a National Assembly firmly controlled by
the Biden Administration, Seoul and Tokyo reversed this
the opposition Minjoo Party (see Figure 1) and with public
trend in 2022 and 2023. In March 2023, the Yoon
approval ratings generally below 40%.
government removed a major source of friction by arranging
for an ROK foundation to compensate the families of South
Figure 1. South Korea’s National Assembly
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. In 2023,
there were seven ROK-Japan heads-of-state meetings (the
first since 2019), multiple ROK-Japan-U.S. summits,
expanded trilateral military exercises, a new trilateral
mechanism to share real time data on DPRK missiles, and a
trilateral “Commitment to Consult” on regional conflicts
Source: National Assembly website, accessed April 5, 2023.
and challenges. Although ROK-Japan relations have
markedly improved, distrust over historical issues lingers.
Mark E. Manyin, Specialist in Asian Affairs
Liana Wong, Analyst in International Trade and Finance
Since Russia’s February 2022 invasion of Ukraine, South
Korea has imposed sanctions against Russia. It has provided
IF10165
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South Korea: Background and U.S. Relations
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https://crsreports.congress.gov | IF10165 · VERSION 43 · UPDATED