When nuclear monitors said Iran had started testing a single advanced centrifuge last year, some U.S. politicians and analysts jumped on the report as proof the Islamic Republic can't be trusted.
To U.S. officials negotiating with Iran, it was probably just a mistake — one that shows the pitfalls in the highly technical accord being discussed. Describing the incident in detail for the first time, U.S. officials, who asked not to be identified following diplomatic rules, said the testing was probably done by a low-level employee on Iran's nuclear program who didn't understand the limits placed on his experimentation.
Diplomats and scientists on Wednesday held a fourth day of talks in Lausanne, Switzerland, as world powers seek an accord to limit Iran's nuclear work. They've given themselves until the end of this month to announce a framework agreement, and until the end of June to work out full technical details.