. A Common External Tariff must be adopted therefore countries must surrender the tariff policies. . Other problems include: overlapping membership (spaghetti bowl), economic imbalances, divergent trade policies and strategies, customs revenue dependence, and varied tariff structures. . A customs union requires a Free Trade Area and a common external tariff. . Achieving a common market by 2015 is a politically difficult step considering that member states have to surrender sovereignty on financial and immigration policies. . A monetary union and a single currency require a common interest rate and fiscal policies.