That is because though Iran finds itself under increased financial pressure from tightening sanctions, officials here argue that their fundamental approach has essentially worked. In continually pushing forward the nuclear activities — increasing enrichment and building a bunker mountain enrichment facility — Iran has in effect forced the West to accept a program it insists is for peaceful purposes. Iranians say their carefully crafted policy has helped move the goal posts in their favor by making enrichment a reality that the West has been unable to stop — and may now be willing, however grudgingly, to accept.

“Without violating any international laws or the nonproliferation treaty, we have managed to bypass the red lines the West created for us,” said Hamidreza Taraghi, an adviser to Iran’s supreme leader, Ayatollah Ali Khamenei, who is close to the negotiating team…

In Tehran, Mr. Taraghi was promoting a narrative that might pave the way for public, and political, acceptance of a compromise over a program that has broad public support, even among competing political factions. Enrichment is seen as a matter of national sovereignty and pride.

Mr. Taraghi ticked off Iran’s successes. First, he said, Western countries did not want Iran to have a nuclear power plant, but its Bushehr reactor was now connected to the national grid. Second, the West had opposed Iran having heavy-water facilities, he said, but it now has one in Arak.