"We have built an advanced manufacturing unit at Isfahan for the fuel plates," Ali-Akbar Salehi said.

"A grand transformation has taken place in the production of [nuclear] plates and rods. With the completion of the unit in Isfahan, we are one of the few countries which can produce fuel rods and fuel plates."

Iran has invited foreign envoys to visit the country's nuclear sites in "a good-will gesture to further prove the peaceful nature of its nuclear activities," Salehi said.

Representatives from Russia, China, the European Union, and the Non-Aligned Movement were invited to tour Iran's nuclear facilities in mid-January.

The West suspects Tehran of pursuing a secret nuclear weapons program, which Iran strongly denies, insisting it needs atomic energy solely for civilian purposes. Iran is currently under four sets of UN sanctions over its refusal to suspend uranium enrichment.