VIENNA -- The chief of the United Nations nuclear agency acknowledged Monday that samples used to determine whether Iran tried to develop a nuclear weapon were collected by the Iranians instead of agency experts, but insisted the probe stands up to strict agency standards.
Such sampling of soil, air or dust from equipment is usually done by the International Atomic Energy Agency's own experts. But agency chief Yukiya Amano confirmed that Iranians carried out that part of the probe at Parchin, where the agency suspects that explosive triggers for nuclear weapons might have been tested in the past.
Diplomats say Iran insisted on the compromise as a condition for any probe of Parchin.
The agency's deputy director general, Tero Varjoranta, said that there have been more than 40 instances of letting a country being inspected use its own staff to do the sampling and that the process is only a small part of a rigid regimen established by the agency to make sure there is no cheating.
He said the criteria at Parchin included: invasive monitoring by video and still cameras while the sampling took place; GPS tracking of the sampling process; International Atomic Energy Agency agreement on where the samples were to be taken; review by unspecified peers of the inspection process; risk assessment and strict observance to make sure that procedures were followed step by step.
"We feel fully confident that the process and the result so far are fully in line with our safeguards practices," he said, standing next to Amano at a Vienna news conference.
Former agency Deputy Director General Olli Heinonen has described Iran as a particularly sensitive case, however, saying he knows of no other case where a country under investigation for possibly trying to make nuclear weapons was permitted to use its own personnel to collect environmental samples as part of the investigation.
The Iran arrangement was first revealed in a confidential draft agreement between the sides seen last month by The Associated Press.
Iran's atomic energy agency spokesman, Behrouz Kalmandi, said International Atomic Energy Agency experts were not physically present during the sampling. But Amano said the procedure meets strict agency criteria that ensure "the integrity of the sampling process and the authenticity of the samples."
Amano spoke a day after he was taken on what Iranian media described as a ceremonial tour of the military site. He told reporters in Vienna that he was able to enter a building that the agency had been observing via satellite and saw signs of "recent renovation work."
He appeared to be referring to the building where the agency suspects that weapons experiments were conducted in the past. The agency has frequently said that subsequent renovation work at and near the building could hamper the agency's probe, a position Amano repeated on Monday.
Amano's visit is part of an assessment due in December that will feed into the deal reached in July between Tehran and six world powers and will help to determine whether sanctions will be lifted.
Iran denies it has ever sought nuclear weapons and insists that Parchin is a conventional military site. Tehran has refused to allow inspections of its military sites as part of the nuclear deal, saying it fears foreign espionage.
White House spokesman Josh Earnest said the Parchin inspection and authentication "disproves the claims of our critics," who said Iran would be conducting self-inspections.
Earnest said that as time goes forward, there will be "many opportunities" to show that the warnings of those who opposed the deal "are eventually disproven based on the way the agreement is implemented."
But some Republican congressional opponents of the July 14 nuclear deal between Iran and six world powers seized on the Parchin inspection as backing their concerns.
Reps. Mike Pompeo, R-Kan.; Peter Roskam, R-Ill.; and Lee Zeldin, R-N.Y., expressed their "grave concern" over what they called Iran's right to "self-inspect." They urged that nuclear-related sanctions be kept in place, at least for now.
But critical legislators have been weakened since the congressional review period of the nuclear deal ended last week.
Information for this article was contributed by Deb Riechmann, Nancy Benac and Donna Cassata of The Associated Press.
A Section on 09/22/2015