An official website of the United States Government Here's how you know

Official websites use .gov

A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS

A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

The Proliferation Security Initiative is a global effort that aims to stop trafficking of weapons of mass destruction, their delivery systems, and related materials to and from states and non-state actors of proliferation concern. Launched on May 31, 2003, U.S. involvement in the PSI stems from the U.S. National Strategy to Combat Weapons of Mass Destruction issued in December 2002. That strategy recognizes the need for more robust tools to stop proliferation of WMD around the world, and specifically identifies interdiction as an area where greater focus will be placed. President Obama strongly supports the PSI. In his April 2009 Prague speech, President Obama first called for the PSI to continue as an enduring international counterproliferation effort. He has subsequently reinforced this as the formal U.S. Government position in significant U.S. policy documents, including the White House’s National Security Strategy and the Pentagon’s Quadrennial Defense Review.

“The PSI is an important tool in our efforts to break up black markets, detect and intercept WMD materials in transit, and use financial tools to disrupt this dangerous trade. It is an innovative and proactive approach to preventing proliferation that relies on voluntary actions by states that are consistent with their national legal authorities and relevant international law and frameworks. PSI participants use existing authorities — national and international — to put an end to WMD-related trafficking.”

When a country endorses PSI, it endorses the PSI Statement of Interdiction Principles, which commit participants to establish a more coordinated and effective basis through which to impede and stop WMD, their delivery systems, and related items. The countries commit to:

  • interdict transfers to and from states and non-state actors of proliferation concern to the extent of their capabilities and legal authorities;
  • develop procedures to facilitate exchange of information with other countries;
  • strengthen national legal authorities to facilitate interdiction; and
  • take specific actions in support of interdiction efforts.
  • The more than 100 countries that have endorsed the PSI so far share a deep concern that WMD, their delivery systems, and related materials could fall into the hands of terrorists. All of these countries have endorsed the effort to make PSI a flexible, voluntary initiative geared toward enhancing individual and collective partner nations’ capabilities to take appropriate and timely actions to meet the fast-moving situations involving proliferation threats.

The United States seeks to strengthen and expand the PSI, ensuring that it remains an effective tool to stop WMD proliferation. We are playing an active role in the success of the PS, by leveraging related counterproliferation efforts across the U.S. government; by contributing diplomatic, financial, military, customs, law enforcement, and other security experts and assets to interdiction exercises; by hosting PSI meetings, workshops, and exercises with other PSI-endorsing states; and by working with specific partner states to improve their capacity for combating the proliferation of WMD.


Afghanistan | Albania | Andorra | Angola | Antigua and Barbuda | Argentina | Armenia | Australia | Austria | Azerbaijan

The Bahamas | Bahrain | Belarus | Belgium | Belize | Bosnia | Brunei Darussalam | Bulgaria

Cambodia | Canada | Chile | Colombia | Croatia | Cyprus | Czech Republic

Denmark | Djibouti | Dominica | Dominican Republic

El Salvador | Estonia

Fiji | Finland | France

Georgia | Germany | Greece

Holy See | Honduras | Hungary

Iceland | Iraq | Ireland | Israel | Italy

Japan | Jordan

Kazakhstan | Kyrgyzstan | Kuwait

Latvia | Liberia | Libya | Liechtenstein | Lithuania | Luxembourg

Malaysia | Malta | Marshall Islands | Moldova | Mongolia | Montenegro | Morocco

The Netherlands | New Zealand | North Macedonia | Norway


Panama | Papua New Guinea | Paraguay | Philippines | Poland | Portugal


Republic of Korea | Romania | Russia

Samoa | Saudi Arabia | San Marino | Serbia | Singapore | Slovakia | Slovenia | Spain | Sri Lanka | St. Lucia | St. Vincent and the Grenadines | Sweden | Switzerland

Tajikistan | Thailand | Trinidad and Tobago | Tunisia | Turkey | Turkmenistan

Ukraine | United Arab Emirates | United Kingdom | United States | Uzbekistan

Vanuatu | Vietnam


U.S. Department of State

The Lessons of 1989: Freedom and Our Future