Tehran has started to install high-tech machines at its main uranium enrichment site in Natanz that are capable of accelerating production of reactor fuel and the core of nuclear warheads, diplomats said on Wednesday.
Iran announced last week that it had begun mounting the new enriching centrifuges, but one diplomat said at the time that the announcement was premature with only a "small number" on site and not yet installed.
Diplomats told news outlets on Wednesday that installation was now well on its way, with inspectors from the International Atomic Energy Agency (IAEA) seeing close to 100 or more machines mounted when they toured the site a few days ago.
The new-generation centrifuges can enrich uranium three to five times faster than Iran's present working model, they said.
Iran recently informed the IAEA that it planned to speed up its uranium enrichment program, using faster and more advanced centrifuges.
A document sent by IAEA officials to news agencies said that Tehran planned to upgrade enrichment equipment at its Natanz plant.
Uranium enrichment is at the heart of the global standoff over Iran's nuclear program, which Israel and much of the West believes is a guise for developing a weapons capability. Iran has denied the allegations.
The latest news about the upgrading comes less than a week before talks between Iran and the P5+1 group -- the United States, Russia, China, Britain, France and Germany -- are to resume in the Kazakh city of Almaty.
Reports last week indicated that during the next round of talks, the West plans to offer to ease sanctions barring trade in gold and other precious metals with Iran in return for Iranian steps to shut down the Fordow uranium enrichment plant.
The underground Fordow facility is carved into a mountain to protect it against possible attacks.
However, an Iranian lawmaker rejected the Western proposal, saying that the Fordow site will never be shut down because that means “helping the Zionist regime to carry out its threats and threaten our facilities.”