Opinions differ as to the cause of the cooling in relations. Iranian explanations include everything from the natural and unavoidable conflict between the Islamic Revolution on the one hand, and perceived American arrogance and desire for global hegemony on the other. Other explanations include the Iranian government's need for an external bogeyman to furnish a pretext for domestic repression against pro-democratic forces and to bind the government to its loyal constituency. The United States attributes the worsening of relations to the 1979–81 Iran hostage crisis, Iran's repeated human rights abuses since the Islamic Revolution, and its growing influence in the Middle East.