What have been the main driving forces of the US foreign policy in the Middle East ?

Abstract

Thanks to a sizeable diplomatic work, the US has gradually become the major foreign power in the Middle East. But, without any former influence in the area, what can have been the main driving forces of the US policy towards the Middle East ? This question obviously implies to know precisely what have been the different interests of the US in the region, but it also leads to think about the difficult yet necessary definition of a hierarchy within those different American interests.