“The sanctions, combined with new trade controls, have made it harder and harder for Iran to get key goods that they need,” said David Albright, a nuclear physicist and the author of “Peddling Peril,” a book on the illicit trade in nuclear components. He notes that as a result of the controls, the Iranians may be running out of maraging steel, a key material for making centrifuges.

And now that it turns out Iran is unlikely to produce nuclear weapons as quickly as was once feared, the Obama administration wants the world to know — as part of its diplomatic strategy to slow Tehran down even more.

“The Iranians have a clear strategy to mislead everybody about how advanced their program is,” the U.S. official said. “We’ve stripped away that mask. This is not a massive program…

“If they think they are within grasp of a nuclear weapons capability, then their natural inclination will be to endure another couple of years of sanctions. But if they think they are still years away and are going to continue suffering economic damage, that makes it much more likely that they would decide, if only for tactical reasons, to accept some limitations on the program.”