International atomic inspectors set foot inside Iran’s bombed Natanz enrichment complex on Friday for the first time since the six-week war began, as parallel talks in Vienna reopened a verification track that diplomats described as the most fragile pillar of the nine-day-old ceasefire.

A six-member team from the International Atomic Energy Agency, led by deputy director-general for safeguards Massimo Aparo, arrived at the site outside the central Iranian city of Kashan shortly before dawn aboard a chartered Iranian air force helicopter from Tehran. The team was accompanied by representatives of the Iranian Atomic Energy Organization and, for the first time since 2019, by two Omani technical observers attached to the Muscat monitoring cell that began standing up earlier this month.

IAEA Director-General Rafael Mariano Grossi, speaking from the agency’s Vienna headquarters, called the access “a long-overdue first step” and said inspectors would spend the weekend cataloging damage to centrifuge cascades and the underground production halls that were struck by Israeli munitions in early April. A second team is expected to travel to the Parchin military complex outside Tehran on Sunday, and a third to the Fordow facility near Qom early next week, he said.

“We are not here to assign blame for the war or for what was destroyed in it,” Grossi said. “We are here to reestablish a verified baseline. Without that baseline, there is no agreement worth signing.”

The visits are the product of nine days of quiet negotiation since the Apr. 15 ceasefire took effect, conducted in parallel with the Muscat follow-on talks that resumed earlier this week. Iranian Foreign Minister Abbas Araghchi, who personally pressed the IAEA invitation during a telephone call with Grossi on Tuesday, told state television Thursday evening that Iran was “willing to demonstrate, with full transparency, what was peaceful and what remains peaceful,” but reiterated that any new restrictions on Iranian enrichment activity would have to be negotiated, not imposed.

Western diplomats described the access as broader than expected. According to two officials briefed on the protocols, IAEA inspectors will be permitted to take environmental swipe samples at all three sites, deploy short-notice remote monitoring cameras to replace those damaged or removed during the war, and request follow-up visits to a fourth, undeclared site near Isfahan that the agency has long flagged. The officials, both speaking on condition of anonymity because the arrangements have not been publicly released, said Tehran had not yet agreed to the Isfahan request but had not refused it either.

In Vienna, the formal verification track resumed Friday morning at the Palais Coburg, the same venue that hosted the original 2015 nuclear talks. Representatives of the so-called E3 — Britain, France and Germany — sat across from an Iranian delegation led by deputy foreign minister Kazem Gharibabadi, with U.S. observers participating in a separate room and shuttling between sessions. China and Russia, which have sought to preserve their roles as guarantors of any new arrangement, sent senior diplomats but did not formally join the opening round.

French Foreign Minister Catherine Colonna, who flew to Vienna for the launch session, said the E3 was working from a six-page framework that built on the Islamabad ceasefire text and on a draft circulated by Oman this week. She said the bloc was prepared to support a phased lifting of war-period sanctions, including European measures on Iranian petrochemicals and aviation insurance, if verification milestones were met on schedule. The first such milestone, she said, would be the completion of the Natanz, Parchin and Fordow inspections by mid-May.

“Europe wants this agreement,” Colonna said. “But Europe will not accept a paper agreement. The inspectors must see what they need to see, and they must see it now.”

The U.S. position remained more guarded. A senior State Department official, speaking on condition of anonymity, said Washington welcomed the resumption of IAEA access but had not committed to any specific sanctions relief and would coordinate closely with Israel before endorsing any framework text. The official said Secretary of State briefed Israeli counterpart Gideon Sa’ar by telephone Thursday night and would travel to Jerusalem early next week. President Donald Trump, asked about the inspections during a brief exchange with reporters at Joint Base Andrews on Thursday evening, said only that “we’ll see what they find, and then we’ll decide.”

Israeli officials have publicly emphasized that any verification regime must include a full accounting of Iran’s pre-war stockpile of 60-percent-enriched uranium, much of which Israeli intelligence believes was relocated in the days before the first airstrikes. Prime Minister’s office spokesman Eylon Levy said in a written statement Friday that Israel “supports inspections and supports their depth,” and that the country’s posture toward any final agreement would be “shaped by what the inspectors are able to verify, not by what diplomats are able to write.”

Analysts cautioned that the inspections, while symbolically important, would not by themselves resolve the underlying questions about Iran’s program. “Natanz was hit hard, but Natanz is not the whole picture,” said Naysan Rafati, senior Iran analyst at the International Crisis Group. “The harder questions are about the material that was moved before the strikes, the centrifuges that were never declared, and the engineering knowledge that survives regardless. Inspections give you a snapshot. They don’t give you a future.”

Rafati said the Vienna track would likely run for at least six weeks before any new framework could be signed, and that the political space for a deal would narrow if violations of the Hormuz ceasefire continued. Two minor incidents, including a Houthi launch from northern Yemen and an unattributed rocket fired toward a U.S. logistics hub in Kuwait, have been reported since the ceasefire took effect, both condemned by Tehran.

Russian Foreign Minister Sergey Lavrov, in a statement issued from Moscow, said Russia was prepared to host a follow-on ministerial in May if the Vienna track produced a draft text, and reiterated Moscow’s offer to take custody of any Iranian enriched uranium above agreed thresholds. Chinese state media reported that Beijing had separately offered to underwrite portions of the verification regime, including satellite imagery and the cost of replacement monitoring equipment.

The Muscat cell, which oversees ceasefire compliance at sea, said in a brief readout Friday that maritime traffic through the Strait of Hormuz had returned to roughly 92 percent of pre-war volume, and that no naval incidents had been reported in the past 72 hours. UN observers in the strait now number 96, the cell said, with two additional patrol vessels expected from Pakistan and Egypt next week.

Inspectors at Natanz were expected to file an initial technical report to Vienna by Sunday evening. Officials at the IAEA said a fuller assessment, including any findings on undeclared material, would be presented to the agency’s Board of Governors at a special session in early June.