LAUSANNE, Switzerland — With substantial progress made on some of the toughest elements of a final nuclear deal in recent weeks, Iran and the six world powers (UN Security Council plus Germany, or P5+1) find themselves struggling to resolve differences over two seemingly more peripheral issues at meetings here this week. They involve the scope of research and development on centrifuges that Iran can conduct during the period of a final nuclear accord, and Iran’s desire for the lifting of UN Security Council sanctions on its nuclear program that it sees as treating Iran as a pariah state.
The hold-up is likely to require negotiators to return next week to try to complete a political accord on major elements of a final nuclear accord that diplomats had hoped to complete this week, ahead of a self-imposed end of March deadline and the threat of new Congressional Iran sanctions.