“They come in and shut us down periodically because they think we are too American,” said Mr. Emami, owner of the ice cream shop.

That is why, Western diplomats in Iran said, the best thing Washington could do to encourage more moderate behavior in Tehran would be to ease off. Less pressure would make it harder for Iran’s leaders to keep out Western influences.

“Take the foot off the gas,” said a diplomat who spoke on condition of anonymity so as not to antagonize the Iranians.

Another obstacle to repairing relations involves the deep internal divisions between Iranians. Those appeared the day after the revolution, when the factions that united to take down the shah could not agree on how to run the country. The Islamists won, and to this day have marginalized those who sought a softer approach.

“Even the ruling elite recognize that there are good things we can get from opening to America,” said a political analyst in Tehran who spoke on condition of anonymity for fear of retribution. But, the analyst said, “We know we have to reconcile internally first.”

The headlines here still focus on conflict: the West’s demands that Iran halt enrichment of nuclear fuel and Tehran’s refusal. Yet the hunger for all things Western is once again breaking through on the streets. The signs tend to be most visible in the north of the city, which has always been wealthier and more oriented toward the West, with sound-alike shops: Starcups and Kabooky Fried Chicken.

“Everyone here is thirsting for American brands, it’s that simple,” said Mehdi Mortazavi, who is helping create Friday’s, a restaurant in Tehran. The sign out front looks just like a T.G.I. Friday’s in the States, with red and white stripes. But the “T.G.I.F.” was dropped because Thursday is the last day of the work week here, and the reference to “God” might not have gone over well. But there will be waiters with suspenders decorated with buttons, Cobb Salad and hamburgers on the menu.