Tehran:  An Iranian news agency says that the country has started using new advanced centrifuges at its main uranium enrichment site.

The semi-official Fars agency reported Wednesday that a "new generation of Iranian centrifuges" had been installed and operated at the Natanz site in the center of the country.

Iran on the same day announced that it had begun loading domestically made nuclear fuel rods into its Tehran research reactor, a defiant move in response to toughening Western sanctions over its controversial nuclear program.

The official IRNA news agency said President Mahmoud Ahmadinejad inserted the first Iranian-made rod into the reactor in northern Tehran, and state TV broadcast live images from the ceremony with Iranian nuclear experts briefing Ahmadinejad on the process.

Iran touted the development as an incremental step in the country's efforts to master the complete nuclear fuel cycle, despite Western penalties and UN sanctions.

The West suspects Iran's nuclear program is aimed at producing atomic weapons, a charge Tehran denies, insisting it's geared for peaceful purposes only, such as energy production. The Tehran reactor, for example, produces nuclear isotopes for treating cancer patients.

Iran has said it is forced to manufacture nuclear fuel rods, which provide fuel for reactors, on its own since international sanctions ban it from buying them on foreign markets. In January, Iran said it had produced its first such fuel rod.

Iran's unchecked pursuit of the nuclear program scuttled negotiations a year ago but Iranian officials last month proposed a return to the talks with the five permanent UN Security Council members plus Germany.

In the past, Iran has angered Western officials by appearing to buy time through opening talks and weighing proposals even while pressing ahead with the nuclear program.

Apart from the EU's recent measures on Iran, which include an oil embargo and a freeze of the country's central bank assets, Washington also recently levied new penalties aimed at limiting Iran's ability to sell oil - which accounts for 80 per cent of its foreign revenue.

Israel is worried Iran could be on the brink of an atomic bomb and many Israeli officials believe sanctions only give Tehran time to move its nuclear program underground, out of reach of Israeli military strikes. The U.S. and its allies argue that Israel should hold off on any military strike on Iranian nuclear facilities to allow more time for sanctions to work.

Tags: Iran nuclear programs, Iran Nuclear reactors, Islamic Republic of Iran, Mahmoud Ahmadinejad