Iran live updates: Trump says Iran will have to agree to 'Major Weapons Inspections'

Vice President JD Vance left the first days of technical negotiations with Iran projecting optimism, telling reporters as he left Switzerland that he felt "great about the progress that we made."

"The fundamental thing we got is, No. 1, we set up the mechanism to ensure not only the Straits of Hormuz are open, but will stay open," Vance said.

"... No. 2, we actually set up the right mechanism to ensure the regional cease fire to manage the inevitable conflicts that will come up," Vance said.

Vance reiterated his earlier comments in which he said Iran will be allowing IAEA inspectors into the country.

Vance said the U.S. will have to “see” what Iran “actually let[s] the inspectors do” once they are in Iran.

“We have the Iranians allowing weapons inspectors, nuclear inspectors into their country for the first time in a long time. We're obviously going to bolster those inspections, that inspection regime, to make sure they can never have a nuclear weapon,” Vance said.

Inspections were part of the Obama-era agreement that Trump canceled during his first term, after which Iran stopped letting international inspectors in.

-ABC News’ Emily Chang, Hannah Demissie and Michelle Stoddart

Hours after Vice President JD Vance announced from Switzerland that Iran agreed to let international nuclear inspectors into the country, President Donald Trump said on social media that Iran will have to "agree to have Major Weapons Inspections" for a long period of time.

"Everybody is fully aware that Iran will agree to have Major Weapons Inspections in order to ensure 'Nuclear Honesty' long into the future," Trump said in the post.

Inspections were part of the Obama-era agreement that Trump canceled during his first term, after which Iran stopped letting international inspectors in.

-ABC News’ Michelle Stoddart

Secretary of State Marco Rubio is scheduled to visit the Middle East this week for the first time since the war with Iran began, with stops planned in the United Arab Emirates, Kuwait and Bahrain, according to the State Department.

He is slated to leave Tuesday and return on Thursday.

-ABC News’ Shannon Kingston

The Trump administration has formally issued a waiver on the sale on Iranian oil, following through on a promise from the Memorandum of Understanding signed by President Donald Trump.

The waiver legalizes the sale of Iranian oil and allows transactions involving vessels that had been previously sanctioned.

The sanctions will be waived for a 60-day period beginning Monday and ending at 12:01 a.m. ET on Aug. 21.

The waiver also allows for "any payment of funds owed to Iran, the Government of Iran, or any blocked person for the purchase of crude oil" to be made in U.S. dollars.

The waiver does not, however, allow the sanctions on Iranian oil to be lifted for people in North Korea, Cuba and parts of Ukraine like Crimea.

-ABC News’ Shannon Kingston and Michelle Stoddart