TEHRAN — All over this city of 12 million people, high-rises are under construction, local engineers and Chinese contractors are rushing to finish a multilevel highway, and the streets are lined with billboards promoting the latest tablets and washing machines made by South Korean companies like Samsung and LG. Supermarkets are fully stocked, and it seems as if new restaurants and fast food joints are opening up every day, and never lacking for customers.

In short, you would not know that oil exports from Iran have dropped by a million barrels a day, and that the free fall in the currency has caused huge inflation — a result of American- and European-led sanctions as well as economic mismanagement by the Iranian government. The West escalated the economic war another notch on Wednesday, imposing a new set of restrictions intended to force Iran into what amounts to a form of barter trade for oil, because payments for oil deliveries can no longer be sent to accounts inside Iran.

A senior Obama administration official called the latest step “a significant turning of the screw,” repeating the administration’s four-year argument that the mullahs here face a “stark choice” between holding on to their nuclear program or reviving their oil revenue, the country’s economic lifeblood.

But there is little confidence among American officials in Washington — and little evidence on the streets of Tehran — that even newly stringent sanctions have much chance of forcing Iran’s supreme leader, Ali Khamenei, into striking the deal that most Americans and Europeans, and even some Israelis, say could defuse the crisis.