That is the last thing Washington wants, in fact, which is is why it has not and will not take it. What Washington wants, instead, is _to ensure that Iraq won't fall into the hands of Iran after it leaves_ -- hence the reluctance to withdraw any time soon.
[WS:] It is the question of 'when" rather that "whether." The Empire did Iran a really big favour by finishing off Iraq. The Empire will leave Iraq when the domestic cost of the occupation become unbearable - it is only the question when. Iran does not have to do anything about it, just sit and wait for the windfall. The Empire knows that, and the only thing it can do is to raise the ante in its dealing with Iran.
The problem the Empire now faces is that Bush administration has no coherent foreign policy after the demise of the Vulcans and their wet dreams of the US hegemony. It is quite clear to me that Bush had no foreign policy whatsoever - he basically let his lieutenants, the relics from the Nixon administration Cheney, Rumsfeld, Wolfowitz et al. to run the show. They fucked up big time and left him with the mess. His current "strategy" is simply to hold on until November 2008 and then pass that mess on someone else. He is pretty much a lame duck doing its best to avoid being shot - not that I feel sorry for him, I only wish that Dems were better shots than Cheney ;).
With that in mind it is likely that the next administration will quickly cut a deal with Iran to "stabilize" Iraq and pull out, perhaps not hanging from helicopters like they did in Vietnam, but more like the Soviets from Afghanistan. And at that point Iran will become - not a friend, to be sure - but a willy nilly collaborator of the Empire.
Sorry to burst your bubble, but I do not see anything progressive about that development, just the Empire getting a black eye and making some minor concessions to a local autocracy. It is not that "Iranian people" have won as you seem to imply, but rather the Empire fucked up (again) and that left some windfall for Iranian autocracy. The only progressive thing coming out of it is that it created a diversion for the Empire to fuck things up elsewhere e.g. Latin America, which is leaning left and flashing its middle finger at the US.
I bet you a beer that Rafsanjani will cry uncle after November 2008, if not sooner.
Wojtek