If world oil production is about to peak (as some of us believe) then it would be vital for the US to be able to exert control over the remaining reserves of easily accessible, high quality crude oil and natural gas, especially so since the neocons are in charge in Washington. The neocons have been preaching a doctrine that the US must ensure it remains the only world super power and that it must use it's military and economic strength to prevent any other countries or alliances accumulating a military powerful enough to challenge that of the USA's armed forces.
Oil is the lifeblood of our modern economies and military machines run on tremendous quantities of oil, not solar power and windmills. If Peak Oil does occur as some predict within the next 5 to 10 years whoever controls the remaining sources of oil will be able to exert enormous control over the rest of the world. Once we are post peak, the trend of oil production will be irreversibly downwards at the same time the growing economies of both rapidly industrializing Asian and already industrialized Western countries continue to demand ever increasing quantities of oil to fuel their economic growth. Without easy access to cheap and reliable energy the world economies will likely go into a tail spin, and as there are no immediate prospects for alternate energy sources to fill in the gap between the supply and demand, it could be a very long and painful recession at best and utter chaos at worse.
For more information on the Neocons see the links on this page:
http://www.tvnewslies.org/html/pnac.htmlFor more information on Peak Oil, just google the term "peak oil" or if you are not at all familiar with term and the implications of the Peak Oil theory, you can go here for a concise intro to the topic.
http://www.energybulletin.net/primer.php