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The Proliferation Security Initiative

The Proliferation Security Initiative (PSI) external link is a global partnership of voluntary cooperation to interdict the transport of biological, chemical, and nuclear weapons, their delivery systems and related materials at sea, in the air or on land to and from actors of proliferation concern. 

The US Department of State describes the PSI as an effort “to involve in some capacity all states that have a stake in nonproliferation and the ability and willingness to take steps to stop the flow of such items at sea, in the air, or on land.  The PSI also seeks cooperation from any state whose vessels, flags, ports, territorial waters, airspace, or land might be used for proliferation purposes by states and non-state actors of proliferation concern.”


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President Bush first announced the PSI on 31 May 2003 as a proactive initiative to respond to the international security challenge posed by the proliferation of chemical, biological, and nuclear weapons, as well as missile technology. 

In September 2003, 11 countries published the PSI Statement of Interdiction Principles, which stipulate legally non-binding guidelines for participating PSI countries.  Because the PSI is not a treaty-based organization, countries may join the US-led counter-proliferation effort by supporting these principles.  The Interdiction Principles define the term “actors of proliferation concern,” and call on states to exchange relevant information and to strengthen existing domestic and international rules and regulations. 

Participating countries can also sign bilateral ship boarding agreements external link that allow partner states to quickly gain access to a ship or aircraft as soon as it enters PSI territory.  The United States has signed such boarding agreements with Croatia external link, Liberia external link, the Marshall Islands external link, and Panama external link.    

The 11 original participating states of PSI are Australia, France, Germany, Italy, Japan, the Netherlands, Poland, Portugal, Spain, the United Kingdom, and the United States.  Canada, Norway, Russia, and Singapore have joined the PSI since its launch in 2003.  Overall, the US claims the support of more than 60 countries that participate in simulation exercises, the first of which began taking place in October 2003.  These exercises, usually hosted or led by a specific country, serve to improve states’ cooperation mechanisms.     

The US asserts the success of the PSI since its inception in 2003, but does not publicize achievements “to ensure the successful future of the PSI.”  The 2003 interdiction of a Libya-bound vessel carrying centrifuge technology is often cited as an example of the success of PSI.  Libya, already engaged in negotiations with the United Kingdom and the United States over its secret nuclear weapons program, renounced its possession of nuclear weapons the same year.   

Some states have criticized the PSI for allegedly violating international law.  In May 2005, Cuba external link stated that the PSI interdiction principles are in violation of a state’s national sovereignty and the United Nations Convention on the Law of the Sea external link.  Likewise, China has questioned the legitimacy of the PSI under international law. 

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