THEY ARE AN ALLY, JUST ONE THAT CAN'T HAVE NUKES:

Iran, US share Afghan goals (David Montero, 5/04/06, The Christian Science Monitor)

The Shiite republic, one of Afghanistan's greatest trading partners, has a visible hand here, building roads and schools, and keeping shops afloat with electricity and goods. What's more, these projects represent only a fraction of the $204 million Iran has spent in aid, ranking it among the top donors to post-conflict Afghanistan.

Even though the US and Iran are locked in an international struggle over Iran's alleged pursuit of nuclear weapons, the long-time foes have worked together well in Afghanistan, a place where they have common ground.