The United States petroleum industry's cost to meet environmental regulations is projected at ten percent of the price per barrel of refined petroleum by the end of the decade.

America is a big user of oil, compared with fuel-efficient Europe, so more dollars than euros flow into the oil-exporters' coffers when oil becomes dear.

Petrol prices in the US, after doubling last year, are now back to relatively cheap rates compared with Europe and Obama would take a big political risk by slapping on big tax rises.