A United Nations atomic agency official recently denied entry into Iran as part of a team investigating suspected bomb research is believed to be an American nuclear weapons expert, diplomatic sources said.
The International Atomic Energy Agency last month said Iran denied a visa for one member of an IAEA delegation that visited Tehran on Aug. 31 to try to advance a long-running inquiry into what the U.N. agency calls the possible military dimensions of the country's nuclear program.
It was the third time the person had been unable to obtain an entry permit, the Vienna-based IAEA said. It did not reveal the official's nationality or expertise.
But the sources, who spoke on condition of anonymity due to the sensitivity of the issue, said they believed he was a U.S. national and an atomic arms expert. The IAEA declined to comment on Thursday.
It is important, the U.N. agency said in a Sept. 5 report on Iran's nuclear program, that "any staff member identified by the agency with the requisite expertise is able to participate in the agency's technical activities".
In a statement distributed to IAEA member states this week, Iran dismissed the criticism of its refusal to let one IAEA expert into the country, saying it had a sovereign right to decide who to admit onto its territory.
But its failure to issue a visa to an IAEA official may deepen longstanding Western suspicions that it is stonewalling the U.N. agency's investigation.
The IAEA has for years been trying to get to the bottom of allegations that Iran has worked on designing a nuclear bomb.