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.
In D.C., there's a belief that Iraqis will tolerate the United States if they can just get the occupation right. But it's the occupation itself that inflames Iraqis' passions.