Updated May 24, 2019
U.S.-Iran Tensions Escalate
Overview
Iranian Reaction
U.S.-Iran tensions have escalated as the Trump
Iran’s leaders have expressed intent to avoid conflict with
Administration took several significant steps in its
the United States while indicating that Iran will respond if
campaign of applying “maximum pressure” on Iran, and
attacked. Some Iranian statements have appeared
Iran responded. U.S. officials state that Iran-linked threats
provocative, including threats by the IRGC Navy
to U.S. forces and interests prompted the Administration to
Commander to close the Strait of Hormuz, but Iran
send additional military assets to the region. Yet, President
historically has issued similar threats that are not followed
Donald Trump, while warning Iran not to take action
by concrete actions. On the other hand, in May 2019,
against the United States, has said he prefers a diplomatic
Iranian Foreign Minister Mohammad Javad Zarif’s
solution that would lower tensions. Members of Congress
proposed negotiations to swap detainees held by both sides.
have received additional information from the
Administration about the causes of the uptick in U.S.-Iran
tensions and Administration planning for further U.S.
[The U.S. military deployments] send a clear
responses. Some in Congress have sought to minimize the
and unmistakable message to the Iranian
potential for the tensions to escalate into conflict.
regime that any attack on United States
interests or on those of our allies will be met
Recent Administration Steps to Pressure Iran
with unrelenting force. Statement by National
The developments that contributed to the tensions include
Security Adviser John Bolton, May 5.
the following:

What they [Iranian leaders] should be doing is
ï‚· On April 8, 2019, the Administration designated the
calling me up, sitting down; we can make a
Islamic Revolutionary Guard Corps (IRGC) as a Foreign
deal, a fair deal. ... We're not looking to hurt
Terrorist Organization (FTO). Iran’s parliament
Iran…But they should call, and if they do, we're
responded by enacting legislation declaring U.S. Central
open to talk to them. President Donald Trump,
Command (CENTCOM) and related forces in the
May 9.
Middle East to be terrorists.

We don’t seek a war, and they don’t either.
ï‚· As of May 2, 2019, the Administration ended a U.S.
They know it’s not in their interests. Iran’s
sanctions exception for the purchase of Iranian oil to try
Supreme Leader Grand Ayatollah Ali Khamene’i, May
to drive Iran’s oil exports to “zero.”
14.
ï‚·
If Iran wants to fight, that will be the official
On May 3, 2019, the Administration ended waivers
end of Iran. Never threaten the United States
under the Iran Freedom and Counter-Proliferation Act
again! President Donald Trump, May 20, 2019
(IFCA, P.L. 112-239) that allow countries to help Iran
remain within stockpile limits set by the 2015 nuclear
agreement (Joint Comprehensive Plan of Action,
On May 8, President Hassan Rouhani announced that Iran
JCPOA).
would no longer abide by JCPOA restrictions on stockpiles
of low-enriched uranium and heavy water. He also
ï‚· On May 5, 2019, citing reports that Iran might be
announced that unless the European Union (EU) countries
preparing its allies to attack U.S. personnel or
that have sought to preserve the JCPOA “fulfill their
installations, National Security Adviser John Bolton
commitments” to provide economic benefits of the JCPOA
announced that the United States was accelerating the
within 60 days, Iran would resume additional aspects of
previously planned deployment of the U.S.S. Abraham
uranium enrichment, including possibly enriching to a
Lincoln Carrier Strike Group to the region and sending a
higher level of purity. On May 22, 2019, Iran’s Supreme
bomber task force to the Persian Gulf region.
Leader, Grand Ayatollah Khamene’i, said he had expressed
to both leaders during JCPOA negotiations that he “did not
ï‚· On May 8, the President issued Executive Order 13871,
really believe” in the way they handled the agreement. The
blocking the U.S.-based property of persons and entities
statement suggests that Iran might pull out of the JCPOA
determined by the Administration to have conducted
entirely and that relatively moderate leaders are in eclipse.
significant transactions with Iran’s iron, steel,
aluminum, or copper sectors.
European Responses
The EU has sought to de-escalate tensions and urged Iran
not to leave the accord entirely. A May 9 joint statement by
the EU and the foreign ministers of France, the United
https://crsreports.congress.gov

---

U.S.-Iran Tensions Escalate
Kingdom, and Germany stated that “We reject any
plan to augment U.S. defense and deterrence against Iran by
ultimatums” by Iran but, “At the same time we recall our
deploying to the Gulf region an additional 900 military
own firm commitments under the agreement including as
personnel, extending the deployment of another 600 that
regards sanctions lifting…” Secretary of State Pompeo
were sent earlier to operate Patriot missile defense
attended meetings with EU officials on May 13, reportedly
equipment, and sending additional combat and
to brief the EU on U.S. information about alleged Iranian
reconnaissance aircraft. Should hostilities erupt, the United
planning for attacks on U.S. interests in the region, but
States has the capability to implement a range of options
press reports indicate that EU officials are skeptical that
such as air strikes on Iranian targets.
actions by Iran represent a materially new threat. UK
Foreign Secretary Jeremy Hunt stated, “We [EU] are very
Status Quo. The tensions could remain, but neither escalate
worried about the risk of a conflict happening by accident,
nor de-escalate, particularly if the U.S.-Iran discourse
with an escalation unintended really on either side.”
remains mostly bellicose but without any significant violent
incidents.
Scenarios and Possible Outcomes
There are several directions the escalating tensions might
De-Escalation. Iran could potentially try to de-escalate,
take, any of which might involve congressional oversight,
perhaps by taking up U.S. offers to negotiate a broader,
potential considerations of new sanctions, authorization or
revised JCPOA, though U.S. demands for a new JCPOA are
limitations on the use of military force, or congressional
extensive and many see that as unlikely. A May 16
steps to support regional partners potentially affected by
Washington Post report indicated that President Trump
conflict. The IRGC’s Qods Force (IRGC-QF) arms, trains,
wants to de-escalate tensions, avoid conflict with Iran, and
and advises allies and proxies throughout the Middle East
negotiate a revised JCPOA. Secretary Pompeo has
region, including in Syria, Lebanon, Iraq, Yemen, and
reportedly sought to establish new channels of contact with
Bahrain. Accordingly, Iran and/or its allies have numerous
Iran via Sultan Qaboos of Oman, whom Pompeo talked
ways to take aggressive action or counter U.S. actions. The
with on this and other issues on May 16, 2019. Iraqi
published State Department report on international
leaders, who say they do not want Iraq to be an arena for
terrorism has consistently asserted that Iran and its key ally,
U.S.-Iran conflict, reportedly dispatched delegations to
Lebanese Hezbollah, have a vast network of agents in
Washington DC and Tehran to try to ease tensions. Yet,
Europe, Latin America, and elsewhere that could act against
Foreign Minister Zarif said publicly in late May that Iran
U.S. personnel and interests far outside the Middle East.
would not engage in new talks with the United States unless
the United States resumes implementing the JCPOA.
With respect to Iraq, on May 15, the State Department
ordered “nonemergency U.S. government employees” to
Potential Implications for Congress of Escalation
leave U.S. diplomatic facilities in Iraq. The move
With the chances of intended or unintended U.S.-Iran
comported with Administration assertions that there is a
conflict seemingly heightened, one question that arises is
heightened threat of Iranian allies acting against the United
that of authorization for the use of military force against
States there. On May 19, a rocket was fired into the
Iran. No legislation has been enacted authorizing the use of
fortified “Green Zone” in Baghdad but caused no injuries or
force against Iran, although successive Presidents have
damage. Iran-backed militias were widely suspected of the
asserted legal and constitutional authority to initiate any
firing, but no U.S. or Iraqi determination of responsibility
military operation. As of late May, several efforts in the
has been announced.
Senate to block the use of funds for offensive U.S. military
action against Iran have not advanced, but further
In the Gulf region, on May 12-13, the United Arab Emirates
legislative efforts reportedly are planned. In addition, the
and Saudi Arabia asserted that four oil tankers and the
Prevention of Unconstitutional War with Iran Act of 2019
Saudi oil pipeline infrastructure had been attacked. Iran
(H.R. 2354/S. 1039) would prevent the use of funds for
denied involvement in the incidents, but a Defense
“kinetic military operations in or against Iran” except to
Department official on May 24 reportedly attributed the
repel or prevent an imminent threat to the United States.
tanker attacks to the IRGC. Some experts assert that the
incidents in the Gulf and in Iraq were orchestrated by Iran
Should the Administration assert authority to use force
to send a message that it can cause instability if provoked.
against Iran, another issue might be the justification for
using existing authorizations. At a Senate Foreign Relations
Escalation. U.S. and Iranian officials have said they do not
Committee hearing on April 10, 2019, Secretary of State
want armed conflict. However, leaders on both sides have
Pompeo, when asked if the Administration considers the
said they will respond with force if the other attacks,
use of force against Iran as authorized, answered that he
increasing the potential for miscalculation to produce
would defer to Administration legal experts on that
conflict. There are over 60,000 U.S. forces deployed to the
question. However, he suggested that the 2001
region, including those stationed at military facilities in the
authorization for force against those responsible for the
Arab states of the Gulf Cooperation Council (GCC: Saudi
September 11 terrorist attacks could potentially apply to
Arabia, Kuwait, UAE, Qatar, Oman, and Bahrain). Press
Iran, asserting that “[Iran has] hosted Al Qaida. They have
reports indicated that the Administration was considering a
permitted Al Qaida to transit their country. There-there’s no
number of options to add forces—with reports ranging from
doubt there is a connection between the Islamic Republic of
a few thousand to several tens of thousands of U.S. military
Iran and Al Qaida. Period. Full stop.”
personnel—to deter Iran from any attacks. On May 24, the
Defense Department said that the President has approved a
Kenneth Katzman, Specialist in Middle Eastern Affairs
https://crsreports.congress.gov

---

U.S.-Iran Tensions Escalate

IF11212


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 | IF11212 · VERSION 2 · UPDATED

---