The New York Times reports: A dispute over what limits should be placed on the development of new types of centrifuges has emerged as a major obstacle as negotiators try to work out an initial accord on Iran’s nuclear program, Western officials said on Thursday.

The negotiators’ goal has been to agree on the outlines of an accord by the end of March that would limit Iran’s nuclear program. A detailed and comprehensive agreement is to be completed by the end of June.

Secretary of State John Kerry told reporters on Thursday that while some progress had been made, the negotiators were still “pushing some tough issues.”

A European negotiator, who asked not to be named while discussing closed talks, was more skeptical, stressing that an accord would not be possible unless the Iranians showed significantly more flexibility over the coming days.

“We are not close to an agreement,” the official said. “We are not there at all.”

Western officials have suggested in recent weeks that the agreement six world powers are negotiating with Iran could allow it to retain and operate about 6,000 centrifuges. [Continue reading…]