Why not? There's nothing to stop them.

Iran nuclear crisis: Fordo capacity doubled - IAEA

The International Atomic Energy Agency (IAEA), the UN's nuclear watchdog, says Iran has doubled production capacity at the Fordo nuclear site, in its latest quarterly report.

The IAEA has also said Iran had "significantly hampered" its ability to inspect the Parchin site.

Iran has produced 189kg (417 lb) of higher-grade enriched uranium since 2010, up from 145kg, it added.

Iran denies its nuclear programme has any military aspect.

The number of enrichment centrifuges at Fordo, at a facility buried deep inside a mountain, had more than doubled to 2,140 from 1,064 in May, the IAEA said.

However, the new machines were not yet operating, it said.

The IAEA said the Parchin site had been "sanitised" and that Iran had "been conducting activities at that location that will significantly hamper the agency's ability to conduct effective verification", if inspectors were granted access.

Iran says it needs nuclear material for energy and medical needs.