There were and always will be the problems,The main factor is trade balance,Countries are always trying to protect balance between import and export,then they set up embargo and tariffs which is very bad decisions for protectionists and countries with cheap labour power,after this the relationships between the countries may be not as good as it was,So then international relations decide a lot in this situation,They create too many international organizations and agreements which may be useful and  peace-maker for this countries.