Initially, the PSI included 11 "core" states (Australia, France, Germany, Japan, the Netherlands, Portugal, Spain, the United Kingdom, the US and Poland). On September 4, 2003, in Paris, these countries detailed the principles governing the PSI in a document titled the "Statement of Interdiction Principles". The document defines the activities which are to be undertaken by the initiative, specifically "to establish a more coordinated and effective basis through which to impede and stop shipments of WMD, delivery systems, and related materials flowing to and from states and non-state actors of proliferation concern, consistent with national legal authorities and relevant international law and frameworks, including the UN Security Council circumstances in which such operations may be carried out (at sea, on land, or in the air) including, most importantly, the requirement that any action taken must be consistent with international law." Since the initial core group of 2003, PSI has expanded to include an "Operational Experts Group" (OEG) of 21 nations as well as 84 other endorsing states. Key states who have endorsed the initiative since its initial founding include major actors in international trade such as Singapore and the United Arab Emirates, as well as countries such as Turkey and the Republic of Korea, who are geographically close to states designated by United Nations Security Council resolutions as proliferation threats.