June 12, 2015
South Korea: Background and U.S. Relations
Overview
alliance, though there have been some delays in
implementation. In 2014, the two countries delayed for the
Since late 2008, relations between the United States and
second time a 2007 agreement to transfer wartime
South Korea (known officially as the Republic of Korea, or
operational control (Opcon) from a U.S. commander to a
ROK) arguably have been the most robust since the
Korean commander, citing the North Korean threat and
formation of the U.S.-ROK alliance in 1953. Cooperation
needed improvements to military interoperability. The U.S.
on North Korea policy has been particularly close, and the
military is in the process of relocating its forces based near
two countries have adjusted the alliance in the face of a
the border with North Korea to new facilities farther south
changing threat from Pyongyang. South Korea also has
on the Korean Peninsula. Seoul has agreed to make its
taken the first steps toward a possible entry into the U.S.-
nascent ballistic missile defense capabilities interoperable
led Trans-Pacific Partnership (TPP) free trade agreement
with U.S. systems but has resisted full integration into the
(FTA) negotiations, which would build on the 2011 United
U.S.-led regional missile defense network.
States-Korea FTA (KORUS FTA). Notwithstanding the
positive state of the relationship, in the coming months
U.S.-South Korea ties could be tested by developments in
areas where the two countries occasionally disagree, such
as how best to handle tense South Korea-Japan relations.
President Park has promoted a number of initiatives with
North Korea that may go against the grain of U.S. policies
increasing pressure on Pyongyang. South Korea also
hesitates to take steps it perceives China could view as
antagonistic, occasionally leading to differences with the
United States.
South Korean President Park was scheduled to travel to the
United States for a summit with President Obama in mid-
June 2015. Less than a week before Park’s scheduled
departure, however, she postponed the trip due to criticism
over her government’s handling of an outbreak of Middle
East Respiratory Syndrome (MERS). The criticism echoes
similar reactions to her government’s response to the April
2014 sinking of a ferry, the Sewol, in which hundreds died.

Park’s approval ratings fell significantly, to near 30%, after
North Korea Policy Coordination
that event and had only just begun to recover when the
MERS outbreak occurred.
Since 2009, in the wake of North Korean provocations
including a long-range ballistic missile test and the
For more, see CRS reports on U.S.-South Korea relations
country’s second nuclear test, Washington and Seoul have
(R41481), the KORUS FTA (RL34330), and U.S.-North
forged a joint approach toward North Korea. In essence, the
Korea relations (R41259).
approach—which many have called “strategic patience”—
U.S.-South Korea Security Relations
contains elements of both pressure and engagement. They
include (1) keeping the door open to multilateral talks
(called the Six-Party Talks) over North Korea’s nuclear
Under the 1953 Mutual Defense Treaty that established the
program but refusing to re-start them without North Korea’s
U.S.-ROK alliance, the United States is committed to
assurance, backed by “meaningful actions,” that it will take
helping South Korea defend itself, particularly against any
“irreversible steps” to denuclearize; (2) encouraging China
aggression from the North. South Korea is included under
to pressure North Korea to denuclearize; and (3) responding
the U.S. “nuclear umbrella” (also known as “extended
to Pyongyang’s provocations by tightening sanctions
deterrence”), and the United States deploys about 28,500
against North Korean entities. The United States and South
troops there. South Korea offsets some of the costs of
Korea have placed significant emphasis on the harder
stationing U.S. armed forces in the country. Under a
elements of their approach, including strengthening their
January 2014 agreement, Seoul agreed to increase its
deterrence posture, calling attention to North Korea’s
annual contributions to about $870 million.
human rights abuses, and refusing to meet North Korean
demands on issues such as scaling back U.S.-ROK military
For the past decade, the United States and South Korea
exercises. Many critics say that the Obama
have been taking steps to transform and modernize the
www.crs.gov | 7-5700

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South Korea: Background and U.S. Relations
Administration’s approach is too passive, with some
concluded negotiations on the text of a new agreement,
arguing that it applies insufficient pressure and others
which is expected to be signed in June 2015. The two states
contending that it provides insufficient incentives for
reportedly have resolved a disagreement over how to treat
Pyongyang to change its behavior.
uranium enrichment and spent fuel reprocessing
technologies. The renewed agreement may contain some
President Park has called for creating a “new era” on the
additional allowances for R&D in South Korea on a
Korean Peninsula by building trust between North and
reprocessing technology called pyroprocessing. The Atomic
South Korea. She has proposed a number of inter-Korean
Energy Act requires U.S. permission before South Korea
projects, exchanges, and dialogues. However, she also has
can reprocess U.S.-origin spent fuel, including spent fuel
stated that a nuclear North Korea “can never be accepted”
from South Korea’s U.S.-designed reactors. The United
and that trust-building with Pyongyang will be impossible if
States’ nonproliferation policies discourage the building of
North Korea cannot keep its international agreements. An
new fuel-making plants in countries that do not already
issue for the Obama Administration and Congress is to
have such plants. The new agreement will go into effect
what extent they will support—or not oppose—Park’s
unless Congress passes a disapproval resolution.
proposed inter-Korean initiatives. Thus far, North Korea
generally has rebuffed Park’s outreach.
U.S.-South Korea Economic Relations
South Korea’s Regional Relations
In 2014, U.S.-South Korea trade was over $110 billion.
South Korea is the sixth-largest U.S. trade partner, while
China’s influence in the region figures into virtually all
the United States is South Korea’s second-largest trade
aspects of South Korean foreign and economic policy. For
partner, behind China. How the countries resolve problems
example, North Korea’s growing economic dependence on
associated with implementing the KORUS FTA may affect
China since the early 2000s has meant that South Korea
South Korea’s potential participation in the TPP talks.
increasingly must factor Beijing’s actions and intentions
South Korea has expressed interest in joining the
into its North Korea policy. As President, Park has held five
negotiations, but it has not officially sought entry. While
meetings with Chinese President Xi Jinping, who has yet to
the United States welcomes South Korea’s eventual
meet with North Korean leader Kim Jong-un. Although
participation, U.S. officials have indicated they will place
Park and Xi describe bilateral ties as having reached an
priority on concluding a TPP agreement among the current
“unprecedented level of strategic understanding,” many
12 negotiating partners before agreeing to the entry of any
analysts expect South Korea will not risk damaging the
new countries. In March 2015, reportedly over the Obama
U.S. alliance to pursue closer relations with China.
Administration’s objections, South Korea announced it was
applying to join the Asian Infrastructure Investment Bank
South Korea’s relations with Japan have been tense since
(AIIB), a new China-led multilateral development bank.
2012, primarily due to differences over how to treat the
1910-1945 period, when Imperial Japan seized and
Figure 1.Party Strength in South Korea’s National
governed the Korean Peninsula. Park has declined to hold a
Assembly
summit with Japanese Prime Minister Shinzo Abe until he
As of May 2015
adopts a “correct understanding” of history. A poor
relationship between Seoul and Tokyo jeopardizes several
important U.S. interests, including trilateral cooperation
over North Korea policy and the ability to respond
effectively to China. Tense relations also complicate
Japan’s plans to expand its military and diplomatic
influence, as well as the creation of an integrated U.S.-
Japan-South Korea ballistic missile defense system, both
goals the Obama Administration generally supports. 2015
marks the 70th anniversary of the end of World War II and

the liberation of the Korean Peninsula from Imperial Japan.
Notes: President Park Geun-hye belongs to the Saenuri (New
Relations between Seoul and Tokyo have improved
Frontier) Party. The last nationwide legislative elections were held in
modestly since the fall of 2014, as Park has adopted a “two
April 2012. The next elections are scheduled for April 2016. South
track” approach—separating disputes over history from
Korea’s next presidential election is scheduled for December 2017.
most other aspects of the relationship—for most bilateral
By law, South Korean presidents are limited to one five-year term.
activities aside from a summit.
Mark E. Manyin, mmanyin@crs.loc.gov, 7-7653
Nuclear Energy Cooperation Agreement Emma Chanlett-Avery, echanlettavery@crs.loc.gov, 7-
7748
In April 2013, the United States and South Korea agreed to
Mary Beth D. Nikitin, mnikitin@crs.loc.gov, 7-7745
a two-year extension of their existing bilateral civil nuclear
Ian E. Rinehart, irinehart@crs.loc.gov, 7-0345
cooperation agreement, also known as a “123 agreement.”
Brock R. Williams, bwilliams@crs.loc.gov, 7-1157
Both the House and Senate adopted the extension by

unanimous consent (P.L. 113-81). It provides a temporary
solution to avoid disruption in nuclear trade. The extension
IF10165
is set to expire in March 2016. The two countries have
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