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Diplomacy in Action

The Proliferation Security Initiative: A Global Cooperative Effort

Fact Sheet
Bureau of International Security and Nonproliferation
April 5, 2013



Launched in Krakow, Poland in May 2003, the Proliferation Security Initiative (PSI) is a global framework of states that commit to disrupt transfers of weapons of mass destruction (WMD), their delivery systems, and related items to and from states and non-state actors of proliferation concern. Not a formal organization, PSI states cooperate to prevent proliferation and strengthen national capacities for action.


Proliferation programs critically rely on shipments of equipment and technology in order to function. The PSI fosters a dynamic, proactive approach to preventing proliferation-related shipments – and thus impeding proliferation programs – through action on a flexible, voluntary basis, consistent with available national authorities and international laws and frameworks.

  • The PSI promotes cooperation by the states best-positioned to act in a given case in their national capacities, using a wide array of military, diplomatic, and law enforcement tools.
  • The PSI also builds states’ capacity to act, including via operational exercises (some 50 to date) and workshops, and via sharing tools and resources to building interdiction-related Critical Capabilities and Practices (CCP).
  • States also work to strengthen interdiction-related authorities on a national or international basis. For example, 11 states have signed bilateral PSI ship boarding agreements with the United States that facilitate securing their consent to inspect vessels suspected of carrying WMD-related cargoes.
  • With all of these steps, states hone their readiness to act to stop WMD-related shipments and fulfill their PSI commitments, as well as signaling on an ongoing basis the resolve of the international community to counter WMD proliferation threats.


States become part of the PSI by publicly endorsing the Statement of Interdiction Principles and thus committing to take action of effectively interdict WMD-related shipments. As of April 1, 2013, 102 states from all regions have endorsed these Principles and now participate in PSI. The United States encourages all states that share the goal of preventing WMD proliferation through effective action to endorse and actively participate in the Initiative.


The proliferation of WMD remains a threat to international peace and security. The PSI remains a high priority component of achieving the international community’s goal of curbing the trade in the world’s deadliest weapons. The PSI continues to expand participation, promote the worldwide development of counter-proliferation authorities and capabilities, and sustain and focus its activities to shape an international environment conducive to WMD-related interdictions.

For more information on the PSI, please visit:

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