The 20 percent level, needed to produce fuel for a medical research reactor, is far below the more than 90 percent required to build a nuclear weapon, but U.S. officials have expressed concern Iran may be moving closer to the ability to reach weapons-grade level.
The United States and its allies accuse Iran of seeking to acquire atomic weapons. Tehran denies the charge, saying its nuclear program is geared toward generating electricity.
Iran has been producing the 20 percent enriched material since February. The new figure of 17 kilograms — about 37 pounds — was announced by Vice President Ali Akbar Salehi, who heads Iran’s nuclear program. That is up from 5 kilograms (11 pounds) Iran announced in April that it had produced so far.
“Potentially, we can produce 5 kilograms a month but we are not in a hurry over this,” Mr. Salehi said, according to the semiofficial Iranian Students News Agency.
The U.N. Security Council approved a resolution two weeks ago strengthening sanctions on Iran over its disputed nuclear program and calling on individual countries and blocs of nations to expand their own sanctions regimes on Iranian individuals and organizations.
The European Union followed with new sanctions, and last week the U.S. Treasury Department said it would restrict economic contacts with some three dozen additional individuals and companies claimed to be helping Iran develop its nuclear and missile programs and evade international penalties.
Iran is producing the further enriched material from its stocks of low enriched uranium, which at 3.5 percent purity is the level needed to fuel an electricity-generating reactor.
Iran says it needs the 20 percent enriched uranium to produce fuel rods to power a research reactor that produces isotopes for treating cancer and other medical material. Salehi said Iran possesses the technology needed to produce the fuel rods and the first should be ready sometime next spring.