Between them, these two new oilfields contain more than double the known U.S. oil reserves. The U.S. currently imports around 10 million barrels a day, half of it from the Western Hemisphere countries of Canada, Mexico and Venezuela. Assume that the remainder could come from Brazil's new fields, which alone would be sufficient to meet U.S. import needs for over 20 years, and some interesting political implications start to emerge.

If the United States can meet all its energy imports needs from its own hemisphere, what would be the effect on U.S. grand strategy, troop deployments and its current role in the Middle East?

A major part of the rationale for the strong U.S. military presence in the Gulf and in the Arabian Sea would disappear. The need to shore up the friendly governments of the Gulf Cooperation Council against the threat of aggression or radical ideology from Iran would be considerably reduced.

The expense of keeping the entire equipment for an armored brigade and an armored Cavalry Regiment in vast warehouses in Qatar, ready to drive direct to battle once the troops and tank crews fly in, would become questionable. The four large merchant vessels that sit off the island of Diego Garcia, available for swift replenishment of a U.S. Marine Expeditionary Force, might well go home.

America's Arab allies may be ill-advised to count on the presence of U.S. forces being permanent. America's enemies in the Middle East might foresee a day in which the Great Satan boards his ships and goes home, leaving the region to its fate.

And what would that fate be? If the main reason for America's military presence in the region has been dependence on oil, there are other oil-hungry powers. The three biggest customers for the oil of the Gulf will be China, Japan and India, and they have a keen a strategic interest in ensuring a reliable supply.

The problem is that there are three of them, and the two most populous, India and China, are developing almost inexhaustible appetites for imported oil. There is already a quiet arms race underway between them in the Indian Ocean, with China building ports that look like naval bases in Pakistan and Myanmar, and India building aircraft carriers. If the Americans turn away, and India and China rush in to fill the vacuum and secure their access to oil, the Arab world may yet come to look back on the American era in the region as a golden age.