Iran has installed 492 new centrifuges at its sensitive Natanz nuclear facility, the official IRNA news agency reported Friday.

"Three new cascades of 164 centrifuges are installed and now operational in Natanz facility," the report quoted an unnamed official as saying.

"The centrifuges are P-1 type," the official added.

P-1 machine is an old design to produce enriched uranium, but just days ago Iranian President Mahmoud Ahmadinejad said his country had tested a new advanced centrifuge which is "smaller" but its capacity "is five times greater than the current machines (P-1)".

Iran has already put 3,000 centrifuges operational at Natanz underground facility since last year and vowed to install 50,000 to produce fuel for a planned network of power plants.

In defiance to the international demands of halting Tehran's nuclear enrichment work, Ahmadinejad on Tuesday said Iran started to install 6,000 new centrifuges at Natanz.

The Friday's announcement of 492 new centrifuges confirmed that Iran is expanding its disputed nuclear program.

However there were rumors that Iran had technical problems running its centrifuges at full capacity, which was denied on Friday by Mohammad Saeedi, the deputy chief of Iran's Atomic Energy Organization.

"There are no technical problems regarding the development of centrifuges," Saeedi was quoted by IRNA as saying.

Hours after Ahmadinejad's speech that Iran has begun installing 6,000 new centrifuges at its uranium enrichment plant, US officials warned that Iran will face new international isolation and sanctions if it refuses to comply with UN Security Council resolutions over its disputed nuclear program.

The United States and its Western allies fear that Tehran is trying to build nuclear weapons. Iran insists that its nuclear program is for peaceful purposes only.

(Xinhua News Agency April 12, 2008)