Western negotiators say they won two important agreements. Iran will allow inspectors to visit the controversial new plant later this month.
Tehran has also agreed in principle for a large part of the uranium it has already enriched at the Natanz plant to be shipped out of Iran. It would then be processed by Russia and France to a higher grade, for use in a research reactor in Tehran which produces medical isotopes.
It is that second agreement that has excited the West. A senior US administration official called it “a positive interim step to help build confidence”.
If the deal is implemented, it could help at least to defer the crisis.