Iran is starting work to install 6,000 new uranium-enriching centrifuges at its nuclear plant in Natanz, President Mahmoud Ahmadinejad announced Tuesday, according to state media.

Iran is starting work to install 6,000 new uranium-enriching centrifuges at its nuclear plant in Natanz, President Mahmoud Ahmadinejad announced Tuesday, according to state media.

"Today, the phase for installing 6,000 new centrifuges at the facility in Natanz has started," the state broadcaster's Web site quoted Ahmadinejad as saying at the atomic plant.

According to the last report by the U.N. nuclear watchdog, Iran has already installed 3,000 centrifuges at Natanz in defiance of Western calls for it to freeze uranium enrichment.

Iran was Tuesday marking its "national day of nuclear technology", which commemorates the April 2006 anniversary of Iran's first production of uranium sufficiently enriched to make atomic fuel.