Print edition: 
WASHINGTON — Iran told the United Nations' nuclear watchdog Monday that it will begin producing purer uranium, a step that experts said could bring Tehran significantly closer to having the fuel for a nuclear weapon.
Iran plans to enrich uranium at its Natanz centrifuge plant to nearly 20 percent purity, a much purer form of the metal than it's achieved thus far, it informed the Vienna-based International Atomic Energy Agency.
If Iran follows through, "it's a really bad development from a proliferation point of view," said David Albright, who closely follows Iran's nuclear development.
Albright, the president of the Washington-based Institute for Science and International Security, said that Iran is three-quarters of the way to producing bomb-grade material from the 3.5 percent pure uranium it now has. Enriching its uranium to 19.75 percent purity, as Iran now has said it will do, "gets them another 20 percent or so" closer, he said.
Iran's decision appeared to kill for now the on-again, off-again deal that was reached in October to ship three-quarters of its nuclear fuel abroad to be refashioned for use in a civilian research reactor.
Iran's leaders insist that the country's nuclear work is for peaceful purposes, and even if the country had bomb-grade fuel, it would need to fashion a nuclear warhead and a means to deliver it to become a nuclear power. Western intelligence agencies say Iranian scientists have worked on both those problems.
Defense Secretary Robert Gates said Monday that there's still a chance that economic sanctions will convince Iran's leaders to change course. He was responding to a question about whether he's concerned that Iran's announcement might provoke an Israeli airstrike on Iran's nuclear facilities.
"Everybody's interest is in seeing this issue resolved without a resort to conflict," Gates said in Paris. "The key is persuading the Iranian leaders that their long-term best interests are best served by not having nuclear weapons."
The U.S., France, Britain and Russia have been discussing a new round of U.N. sanctions on Iran, but China, the other veto-holding member of the U.N. Security Council, has balked, arguing that more negotiations are needed.
