Vice President JD Vance cast the first day of high-level negotiations with Iran as productive on Monday, saying the two sides had laid a “good foundation” in Switzerland that would allow technical discussions to continue in his absence.

At a news briefing after the talks ended in the Swiss resort town of Bürgenstock, Mr. Vance claimed the talks had yielded consensus on at least one issue — international access to Iranian nuclear sites — as well as progress in several technical areas.

“The Iranians have agreed to invite I.A.E.A. inspectors back into their country,” Mr. Vance said, referring to the International Atomic Energy Agency, the U.N.’s nuclear watchdog, welcoming it as a “first step toward permanently ending a nuclear weapons program in Iran.”

However, a spokesman for Iran’s foreign ministry, Esmail Baghaei, told the official Iranian state news agency IRNA that Iran had made “no new commitments” for inspections.

Iran allowed international inspections under the 2015 deal limiting its nuclear program. But it restricted inspections after President Trump withdrew from that agreement in 2018, and excluded independent inspectors last year after U.S.-Israeli attacks on the country’s nuclear sites.

The United States is seeking assurances from Iran that it cannot covertly develop nuclear weapons as part of the final deal, which the two sides are aiming to hammer out in 60 days. Iran has always insisted that it was not seeking such weapons, but it has enriched uranium close to the levels used in atomic bombs, far beyond what is needed for civilian uses.

In Monday’s briefing, Mr. Vance also appeared to confirm the establishment of several technical mechanisms to govern the talks, following a similar overnight announcement by Pakistani and Qatari mediators.

Mr. Vance said the two sides had agreed to form an oversight process for the technical negotiations, allowing lower-level negotiators to continue talks in Switzerland in the absence of himself and the senior Iranian delegation, led by Mohammad Bagher Ghalibaf, the speaker of the Iranian Parliament.

The vice president also said the sides had agreed to establish separate coordination channels for de-escalating conflicts arising in the Strait of Hormuz and Lebanon. The mechanisms, which Mr. Vance did not elaborate in detail, appeared to match the ones outlined in the mediators’ statement.

The possibility of renewed conflicts in the strait, a critical waterway that was a conduit for as much as one-fifth of the world’s oil and natural gas before the war, and Lebanon, where Israel is attacking Iranian-backed Hezbollah militants, have already threatened to derail the nascent talks.

Referring to the waterway, Mr. Vance said that the “coordination mechanism” would ensure that “when there are the conflicts that inevitably come up, we can make sure we work through them.”

He said a similar mechanism had been established in Lebanon to help avoid miscommunications between Hezbollah and Israel, reducing the risk that isolated hostilities would escalate. A cease-fire is supposed to be in place in Lebanon, but as with previous truces, it has reduced clashes without ending them.

“Israel and every nation in the region has the right of self-defense,” said Mr. Vance. But “if the conflict spirals out of control, that’s worse for everybody’s self defense.” The de-confliction channel became operational as of 4 p.m. in Switzerland, or 10 p.m. Eastern time, on Sunday, he said.

At the news briefing, Mr. Vance also floated a U.S. proposal for unfreezing billions of dollars in Iranian assets, a core demand of Tehran in the negotiations. Under the proposal, which Mr. Vance credited to President Trump’s son-in-law Jared Kushner, any unfrozen Iranian assets would be spent on U.S. goods, such as soy, corn and wheat.

He said that the United States and Qatar would oversee the process of unfreezing the assets, which would be prohibited from being used to fund terrorism. “If Iranian assets are ever unfrozen, they’re going to go to make American farmers richer and to feed the Iranian people,” he said.

On Monday afternoon, Iranian officials had yet to comment on the proposal.