The world today is the word of governments (states) whose major constituent is nations, or rather, human agents. The world of Islam, being comprised of about 50 Islamic countries with defined international borders, witnesses small and big states which are overshadowed by the binding rules and regulations of international law which exert impacts on the relations of Muslim nations with each other and with other non-Muslim nations. The main question is that whether or not it is possible to propose the theory of a single religious state and put it into practice with the present age of separate national states. The findings of this research work show that, given the existing realities, international binding rules and regulations, and the present conditions of Islamic countries, it seems almost impossible to realize the idea of a single unified Islamic state before the reappearance of Imam Mahdi (May God’s peace be upon him). However, instead of the existing nation-states which are not recognized by Islam, and of the ideal single Muslim community-state whose realization seems to be impossible under the circumstances, one can suggest one possible alternative; an idea which can be realized, both in theory and in practice, by establishing a limited (small) unified state or a big unified state being comprised of a number of Islamic states or a union of Islamic countries. This can pave the ground to take gradual steps to the ideal Islamic state after having taken some qualitative and quantitative courses of development. The article, enumerating the four obstacles in the way of establishing a united Islamic state, seeks to study the grounds and strategies of promoting greater unity in the world of Islam.