The United Nations nuclear watchdog said it is satisfied with access Iran will grant it to the country's Parchin military site, suspected by some states to have in the past hosted atomic bomb-related experiments.
Without International Atomic Energy Agency (IAEA) confirmation that Iran is keeping promises enshrined in a landmark nuclear deal reached with world powers on July 14, the country will not be granted much-needed relief from sanctions.
According to data given to the IAEA by some member states, Parchin might have housed hydrodynamic experiments to assess how specific materials react under high pressure, such as in a nuclear blast.
Asked if Iran would be allowed to conduct inspections itself to address concerns about Parchin, the IAEA said it was legally bound to keep its arrangements with Tehran confidential.
"The separate arrangements of the roadmap are consistent with the IAEA verification practice and they meet the IAEA requirements," Serge Gas, a spokesman for the agency, said in a statement.
Under a roadmap agreement Iran reached alongside the political deal, Iran is required to give the IAEA enough information about its past nuclear programme to allow the watchdog to write a report on the issue by year-end.
For months, Iran had been stalling an IAEA investigation into the possible military aspects of its past nuclear activities, relating mostly to the period before 2003, saying the agency's data for its investigation was fabricated.
Iran says its nuclear programme has no military dimensions.
The IAEA says it repeatedly asked for access to Parchin.
Republican U.S. Senator Lindsey Graham, who chairs a committee overseeing his country's financial contribution to the IAEA, has said he would push to stop such money if the agency does not publish its arrangements with Iran.