"Very few sanctions regimes have actually produced regime change or altered regime behavior. The US could not even accomplish this goal with regard to a small island 90 miles off its shores, Cuba. That an oil giant half way around the world with a population of 70 million that is as big as Spain, France and Germany can be effectively bludgeoned with sanctions is not very likely."That doesn't mean the U.S. won't still press ahead with sanction plans. But arm-twisting other nations and firms not to buy Iranian petroleum and gas may be a lot harder than it seemed only a few months earlier. For comparison purposes, check out the conclusions of this earlier GAO report measuring the effectiveness of the ban on U.S. trade and investment with Iran between 2003 and 2007.
"The US needs to engage in comprehensive security talks with Iran, in hopes of striking a grand bargain. Because as Admiral Mullen rightly says, there are no good military options here."