Kaveh L Afrasiabi's Asia Times article "Iran woos Farsi-speaking nations" suggests that, following in the steps of the Francophonie and the Community of Portuguese Language Countries, speakers of the Farsi might now be close to claiming a multinational language association of their own. Drawing on the very strong similarities if not outright identity between Farsi and Afghanistan's Dari and Tajik, Iran might be in the process of using a common language to cement an economic community under the aegis of the Economic Cooperation Organization (Wikipedia, official site). Of course, this all has to fit into the Great Game.
Apart from the potential of growing international competition in the region based on the ties of different powers' linguistic and cultural links with the peoples of Central Asia, the main problem facing this project is the United States. As one might expect, the United States is rather hostile to the idea of an Iranian-led bloc including Afghanistan.
One initiative in particular that Iran is genuinely interested in, and hopeful about its prospects, deals with trilateral cooperation among the three Farsi-speaking nations of Iran, Afghanistan and Tajikistan. Such a union, if formed in the (intermediate) future, will definitely enhance Iran's regional status and create new linkages between Iran and Central Asia and beyond.
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[T]he ECO-based initiative to enhance cooperation among the Farsi-speaking nations has a definite geocultural dimension or ramification, at least as far as Turkey and other Turkish-speaking ECO members are concerned. Iran has always been suspicious of Turkey's, or for that matter Kazakhstan's, attempts to forge closer ties to the Turkish-speaking Azerbaijan and the Turkish-speaking Central Asian states; such attempts, particularly by Turkey during the early and mid-1990s, were perceived as being directly anti-Iranian in nature.
Since then, mutual fears and concerns of pan-Turkism and pan-Persianism have been much dissipated by the growing maturity of Iran-Turkey and Iran-Azerbaijan relations in particular, based on mutual and shared interests, and the initial sound and fury of a "new great game" in Central Asia and the Caucasus has been replaced by the cold, realistic logic of cooperation and interdependence.
Apart from the potential of growing international competition in the region based on the ties of different powers' linguistic and cultural links with the peoples of Central Asia, the main problem facing this project is the United States. As one might expect, the United States is rather hostile to the idea of an Iranian-led bloc including Afghanistan.