Iran has opened its main uranium enrichment plant to a visiting foreign leader for the first time in the history of the site.
State TV on Monday showed footage of Mongolia's President Tsakhia Elbegdorj inspecting centrifuges at a facility in the central Iranian town of Natanz.
Inspectors of the International Atomic Energy Agency visit the site regularly, and Iran has in the past allowed foreign diplomats and reporters to visit it as well.
The broadcast says President Elbegdorj said it would not be possible to visit such a sensitive place in other countries.
Last week, Iran denied it had plans to show its nuclear sites to diplomats visiting Tehran for this week's Non-Aligned Movement (NAM) summit, despite an earlier offer by a deputy foreign minister.
Iranian Deputy Foreign Minister Mohammad Mehdi Akhoundzadeh hinted earlier that visiting NAM diplomats might be allowed to tour the Parchin military base, which the UN nuclear watchdog says may have been used for nuclear-related explosives trials.
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