If Iran can manage to push the uranium to 20 percent on its own, and it is not clear that it can, Western scientists say it could also likely enrich it to weapons grade.

Iran denies its nuclear program has a military component, and says the enrichment is for fuel for a Tehran reactor that makes medical isotopes. It worries it would not get the uranium back if it sends it overseas.

Nuclear chief Salehi said Iran would readily stop the enrichment if the West were to give it the fuel.

Salehi told al-Alam the offer is still open and that once Iran receives the fuel, it will stop the enrichment.

Western countries, in particular the United States, say the original deal was not meant to be modified and are pushing for further U.N. sanctions.

U.S. Defense Secretary Robert Gates says there is still time for sanctions to work.

Meanwhile, with tensions over the standoff rising, Iranian Defense Minister Ahmad Vahidi said Iran has begun production of two types of unmanned aircraft with surveillance and attack capabilities.

Vahidi said the drones can carry out assaults with high precision.

Iranian Air Force commander Hesmatollah Kassiri was quoted as saying Iran is working on a new air-defense system. The commander said Russia has been slow to deliver its S-300 missiles as agreed, but Iran's domestically-built system will be as powerful or even stronger.

Iran frequently announces major advances in its military, nuclear and space programs. The latest advances have not been independently confirmed.