The United States and Iran concluded the second round of diplomatic talks on Tehran's nuclear activities, setting the agenda for swift negotiations that, according to Iran, will not require dismantling the country's comprehensive nuclear infrastructure.

Instead, according to Iranian Foreign Minister Abbas Araqchi, a group of experts will meet next week to discuss technical details, including the maximum levels to which Iran can enrich uranium, the size of the nuclear stockpile it can maintain, and how to monitor and verify compliance with any agreement.

But these talks, experts say, implicitly assume that President Donald Trump is willing to back down from the administration's original insistence that all of Iran's major nuclear sites and long-range missile arsenals undergo what National Security Advisor Michael Waltz recently called "complete dismantlement."

Since then, US administration officials have been at odds over the goals of their talks with Iran, and over whether it is acceptable to allow Tehran any capacity to enrich uranium—and thus race toward a nuclear bomb.

In private talks, the Iranians informed US officials of their willingness to reduce enrichment levels to the levels established in the 2015 agreement reached with the administration of former President Barack Obama. This agreement limited the amount of nuclear material Iran could possess and restricted enrichment to 3.67%, the level needed to produce fuel for nuclear power plants.

But Trump withdrew from that agreement in May 2018. Over the past three years, Iran has been enriching uranium to much higher levels: around 60% purity, just below the level needed to produce a nuclear weapon. This presents Tehran with two options: either race to produce weapons-grade fuel, or negotiate with the United States to return to the original levels stipulated in the agreement with the Obama administration.

Steve Witkoff, the chief US negotiator, expressed his willingness to pursue this path earlier this week. But this has exposed Mr. Trump to criticism that after declaring the decade-old nuclear agreement a "disaster" and scrapping it, he has not gotten anything better.

Witkoff was forced to back down. He posted on social media that the US position now was that "Iran must halt and eliminate its nuclear enrichment and weapons program." The key word was "eliminate."

Witkoff did not speak immediately after the negotiations—the second round in two weeks—ended on Saturday afternoon in Rome. Oman, which is mediating the talks, said those technical negotiations would be held in Muscat, its capital, in the coming days. When asked this week whether the United States could live with Iran's limited nuclear enrichment capacity, American officials evaded the answer, saying only that Mr. Trump had pledged not to allow Iran to acquire a nuclear weapon.

Witkoff will now have to brief Trump and his administration colleagues on the latest round of talks. According to the New York Times, officials familiar with the internal debate say that National Security Advisor Waltz and Secretary of State Marco Rubio, both of whom were staunch critics of the Obama-era nuclear deal when they were members of Congress, still oppose allowing Iran to possess any nuclear production capacity.

Rubio stated on Friday that any agreement must prevent Iran from obtaining a nuclear weapon. He told reporters on a trip to Paris, "It has to be something that not only prevents Iran from having a nuclear weapon now, but also in the future."

But Witkoff, like Obama's negotiators a decade ago, apparently concluded that the only way to reach an agreement was to allow some enrichment capacity, subject to monitoring and verification by American or international inspectors.

Israel has long relied on President Trump to take a tough stance against Iran. During his first term, he did just that, ordering the killing of Iran's top security official, Qassem Soleimani, devastating Tehran's economy with US sanctions, and abandoning an international agreement limiting Iran's nuclear program. But now, as Trump resists being dragged into a new war in the Middle East, he is trying to take a more measured approach.

While the specter of military action remains—Trump said last week, “If we have to take very severe action, we will take it”—he has moved forward with negotiations, reportedly asking Israel to refrain from attacking Iranian nuclear sites.

All this has put Israel in a state of tension regarding the course of the talks.

Iranian Foreign Minister Araghchi explained that the goal is to reach a "logical and rational understanding, while respecting the legitimate rights of the Islamic Republic of Iran and lifting harsh and illegal sanctions, that will remove any doubts about Iran's peaceful nuclear program."

Iran also lowered its expectations for a resumption of diplomatic efforts within the next two months, under a deadline set by Trump.

"This matter must be monitored carefully. The red lines are clear. They are clear to the other side, and they are clear to us as well," Iranian Supreme Leader Ayatollah Ali Khamenei said in a statement posted on social media on Tuesday.

He said he was "neither overly optimistic nor pessimistic" about the process, but described the first round of indirect talks as good.

Iran maintains that its nuclear program is legal and intended solely for civilian uses, such as energy and medical isotopes. It refuses to halt uranium enrichment, the material needed to build a nuclear bomb.

For more than a decade, world leaders have sought to limit Iran's uranium enrichment to levels far below those needed for weapons. This requires independent verification by outside inspectors. On Wednesday, the head of the UN's International Atomic Energy Agency, Rafael Grossi, visited Tehran to urge its leaders to cooperate.

Scientists believe Iran is closer than ever to being able to produce six or more nuclear weapons within months, or possibly a year.

After meeting last week with Iranian Foreign Minister Araghchi, Witkoff suggested that Iran might be able to produce low levels of uranium under a verification regime that also extended to Tehran's missile program. However, Mr. Witkoff shifted his position to insist that "Iran must halt and eliminate its nuclear enrichment and weapons programs" to conclude any agreement.

Experts say Witkoff's shift reflects uncertainty within the Trump administration—and likely within the president himself—about whether it believes it can strike a reasonable deal.

Some believe the Trump administration may be open to allowing low-level enrichment as long as Iran makes an unprecedented concession, such as opening its nuclear sites to US inspectors or welcoming US investors.