But while that is a new element in the talks, the cultural divide in how to negotiate is not.

That divide was evident 11 years ago, in the gilded halls of the 160-year-old Beau-Rivage Palace Hotel in Lausanne, Switzerland, where Secretary of State John Kerry and his counterparts from five other countries struggled to close a preliminary agreement with Iran. It was, perhaps, the closest analogue to what is unfolding now in Islamabad.

Every day the American delegation would speak about how many centrifuges had to be disassembled and how much uranium needed to be shipped out of country. Yet when Iranian officials — including Abbas Araghchi, now the Iranian foreign minister — stepped out of the elegant, chandeliered rooms to brief reporters, most of the questions about those details were waved away. The Iranians talked about preserving respect for their rights and Iran’s sovereignty.

“I remember we finally got the parameters agreed upon at the hotel,” Wendy Sherman, the chief U.S. negotiator at the time, said on Monday. “And then a few days later the supreme leader came out and said, ‘Actually, some very different terms were required.’”

Ms. Sherman, who went on to become deputy secretary of state in the Biden administration, would go into these negotiations with a large posse. She often had the C.I.A.’s top Iran expert in the room, or nearby. So was the energy secretary, Ernest Moniz, an expert in nuclear weapons design. Proposals floated by the Iranians would be sent back to the U.S. national laboratories, where weapons are designed and tested, for expert analysis of whether the agreements being discussed would keep Iran at least a year away from a bomb.

But Mr. Trump’s negotiating team travels light, with no entourage of experts and few briefings. Jared Kushner and Steve Witkoff, the president’s son-in-law and the special envoy, learned their negotiating skills in New York real estate and say a deal is a deal. They say they have immersed themselves in the details of the Iran program, and know it well.