Gareth Porter is an investigative historian and journalist specialising in U.S. national security policy. The paperback edition of his latest book, "Perils of Dominance: Imbalance of Power and the Road to War in Vietnam", was published in 2006.
While U.S. officials try to gin up a war with Iran by accusing it of meddling in Iraq's affairs, their real problem is that al Sadr's Mahdi army is determined to end the occupation and is simply too big to be beaten by military force.
The charge that Tehran is using Iran's elite Quds Force to fight a proxy war in Iraq does not ring true, as even the United States' top man in Iraq, General David Petraeus, has conceded.
Militant Shiites hold the high cards in any showdown against the U.S. occupying forces -- continued attacks against them would be a decisive defeat for the occupation.