Iran said Wednesday it has almost doubled its stockpile of uranium that the country began enriching to higher levels earlier this year in defiance of U.N. demands to halt the program.
Nuclear chief Vice President Ali Akbar Salehi said Iran now has 30 kilograms, or about 66 pounds, of uranium enriched to 20 percent _ almost twice the amount reported in June.
The 20 percent level is enough to produce fuel for a medical research reactor but far below the more than 90 percent enriched uranium required to build fissile material for nuclear warheads.
However, U.S. officials have expressed concern Iran may be moving closer to the ability to reach weapons-grade level.
Iran's refusal to stop enriching uranium lies at the heart of its dispute with the West over Tehran's nuclear program. Iran insists on its right under the Nuclear Nonproliferation Treaty to enrich uranium and produce nuclear fuel, and has vowed never to give up the program.
The United States and some of its allies accuse Iran of using its civilian nuclear program as a cover to develop atomic weapons. Tehran has denied the charges, saying its nuclear program is geared toward generating electricity and producing nuclear medical radioisotopes, not nuclear bombs.
Iran started producing the 20 percent enriched material in February and in June reported having stockpiled 17 kilograms _ or about 37 pounds. Iranian nuclear officials at the time said the production rate was about three kilograms (6.6 pounds) of the material each month.
"So far, nearly 30 kilograms of 20 percent enriched uranium has been produced," Salehi was quoted as saying by the semi-official ISNA news agency.
This summer, the U.N. Security Council imposed a fourth round of sanctions against Iran over its refusal to halt the enrichment technology.
Iran is producing the 20 percent level from its own stocks of low enriched uranium, which has a 3.5 percent purity and is needed to fuel an electricity-generating reactor.
Iran says it needs the higher level of 20 percent enriched uranium to produce fuel rods to power a research reactor that produces isotopes used in cancer treatment and other medical material.
Iran also claims it has the technology _ which few countries have _ needed to produce the fuel rods and that the first rod should be ready within a year.