A secretive military facility in the desert near Tehran has become the focus of pitched debate over the Iran nuclear deal as critics work to derail the agreement ahead of next month’s vote in Congress.

President Barack Obama has won the backing of several key lawmakers in recent days, boosting White House hopes that the nuclear deal will survive the vote. But Obama officials are nervous that the latest debate about the military facility at Parchin — which they say is fueled by distortions — could blunt their momentum.


The debate touches on larger questions about the deal, including whether Iran should be forced to grant unrestricted outsider access to any site on its soil. Supporters of the deal say no country not under military occupation would allow such a thing. It also resurrects the long-standing question of whether Iran should be forced to publicly confess its past nuclear weapons research, another demand Obama officials call unrealistic.

This week, critics pounced on a report that the nuclear deal will allow Iran to provide its own environmental samples from Parchin for testing to determine whether the facility was once used to study nuclear weapons designs.

“The Obama administration has a lot of explaining to do,” House Speaker John Boehner said in a statement. “Why should Iran be trusted to carry out its own nuclear inspections at a military site it tried to hide from the world?” Republican Senator Lindsey Graham added that “[a]llowing the Iranians to inspect their own nuclear sites, particularly a notorious military site, is like allowing the inmates to run the jail.”

The nuclear deal with Iran struck on July 14 by the U.S. and five other world powers imposes limits designed to keep Iran at least one year from a potential bomb in return for lifting economic sanctions.

Obama officials insist the debate over Parchin is overblown, arguing that western intelligence has already provided a clear picture of Iran’s past activity at the site. Particularly given that Iran has repeatedly bulldozed and paved over the suspected testing areas over the past decade, they doubt any new sampling will advance their understanding of Iran’s past nuclear activities there.

They also argue that statements like Boehner’s and McCain’s misleadingly blur the issue of Iran’s past research at the single military complex with the much broader challenge of monitoring all of Iran’s possible nuclear sites in the years ahead.

“Let’s be clear — this issue is one of past behavior,” said a senior administration official. “The United States has already made our judgment about the past, and we are focused on going forward.”

Parchin may seem an unlikely source of controversy, given that it contains no nuclear material and that U.S. officials believe that nuclear-related work stopped there more than a decade ago.

The sprawling complex, composed of hundreds of buildings and test sites 20 miles southeast of Tehran, researches and develops explosives and rockets for Iran’s military. It houses none of the uranium-enriching centrifuges that became famous during the nuclear negotiations.

But intelligence officials believe that Parchin has played an important past role in Iran’s nuclear program — and could do so again. Western intelligence has found that Iran conducted explosive tests there in 2000 as part of a since-discontinued effort to master warhead construction. Specifically, the International Atomic Energy Agency (IAEA) says that Iran constructed a containment vessel at Parchin which it used to test explosive compression, a technique for triggering an uncontrolled chain reaction in fissile material like highly enriched uranium.

For Iran, scrutiny of Parchin is an extremely touchy matter. Tehran insists its nuclear program has always been peaceful, and Iran’s Supreme Leader has issued a religious fatwa saying that Islam forbids production of nuclear weapons. As a result, sources who worked on the Iran nuclear deal say, there was little chance Iran would ever come clean about its weapons research at the site.

The question of outsider access to Parchin is equally fraught within Iran. Conservatives in Iran, especially in the country’s military establishment, are hostile to IAEA inspectors, whom they have accused of of passing intelligence to the U.S. and Israel to facilitate sabotage and assassinations.

Their fears may have been stoked by a massive October 2014 explosion at Parchin, whose cause was never clearly explained.

In June, Secretary of State John Kerry seemed to downplay the importance of confirming that past research. “We’re not fixated on Iran specifically accounting for what they did at one point in time or another,” Kerry said. “We know what they did. We have no doubt. We have absolute knowledge with respect to the certain military activities they were engaged in.”

Even so, the nuclear deal required Iran to strike a parallel agreement with the IAEA to resolve the United Nations atomic watchdog agency’s outstanding questions about the Parchin site. The deal did not specify exactly how that would happen, however, and the IAEA says its agreements are confidential. That has drawn attacks from Republicans who complain about what they call “secret side deals” between Tehran and the agency.

The Associated Press said its report was based on the partial text of Iran’s agreement with the IAEA, which it said allowed Iran to take environmental samples from Parchin, according to text the AP posted, “using Iran’s authenticated equipment, consistent with technical specifications provided by the Agency, and the Agency’s containers and seals.”

In a Thursday statement, the IAEA’s director general, Yukiya Amano, did not deny the specifics of the report, but said he was “disturbed by statements suggesting that the IAEA has given responsibility for nuclear inspections to Iran.”

Amano’s language hinted at the difference between the one-time inspection — to address his agency’s questions about past work at Parchin — and the IAEA’s mandate to monitor and inspect any known or suspected Iranian nuclear facilities over the next 15 years.

The AP report suggested that IAEA inspectors would not be allowed to physically enter the base, though the Iranians will provide photos and video of their samples. The IAEA typically analyzes such samples to check for the presence of radioactive materials and other telltale substances associated with nuclear research.

Intelligence officials and commercial satellite imagery show extensive bulldozing, repaving and other suspicious activity at Parchin in recent years. Critics of the nuclear deal were inflamed just two weeks ago after the Institute for Science and International Security, a think tank with expertise on Iran’s nuclear program, said satellite images showed that Iran was likely continuing its efforts to hide traces of its past work even after the nuclear deal was signed.

Sources said that the IAEA’s arrangement with Iran came as no surprise to Obama officials, who considered it carefully during the nuclear negotiations in Switzerland, and consulted with intelligence officials and U.S. nuclear scientists. Opponents of the deal counter that the Obama administration was foolhardy not to demand more access and information about Parchin, insisting that containing Iran’s nuclear ambitions requires perfect knowledge about its past activity — and that allowing Iran to pretend it never conducted nuclear weapons research sets a dangerous precedent for future nonproliferation efforts.

Still unclear is whether Iran has made any specific agreement regarding possible IAEA requests to inspect Parchin in the future, should it believe that Iran has resumed its weapons research there. The nuclear deal requires Iran to give inspectors prompt access to any suspicious sites on request, with disputes referred to an arbitration panel in a process that can take up to 24 days to resolve.

Congress is expected to vote on the deal in mid-September and a vote of disapproval could restrict Obama from lifting sanctions on Iran. With Republicans unified against the deal, it faces majority opposition in both chambers. But Obama is expected to veto the measure, and administration officials believe they can fend off any effort to override that veto.

In recent days the deal’s supporters have grown hopeful about averting even an initial vote of disapproval through a Senate filibuster. That prospect looked likelier after Thursday’s declaration of support for the deal by the centrist Democratic Senator Claire McCaskill of Missouri. On the House side, Democratic Rep. Jerrold Nadler of New York announced his support for the deal, a significant move given that he represents a heavily Jewish area. Israel’s government is strongly opposed to the nuclear deal.