The United Nations' International Atomic Energy Agency (IAEA) suspects nuclear weapons-related research may have taken place at the Parchin military complex southeast of Tehran.
Iran has dismissed the allegations but has yet to allow the agency to visit the facility, despite repeated requests.
When Iran is ready, they will offer the washed site up for inspections. That offer will be called by the West a great breakthrough in building confidence.
And when the site is inspected, the lack of clear evidence that the site was used for nuclear weapons research will be used as proof that Iran is not pursuing nuclear weapons capabilities.
And Iran will have bought even more time.
Remember, while we debate how far away Iran is from nuclear weapons, Iran is on a path to get nuclear weapons. Unless we have plans to do something, mullah-run Iran will have nuclear weapons when the reach the end of that path, no matter how long it takes.