LAUSANNE, Switzerland — Iran and the six world powers (the five permanent UN Security Council members plus Germany, or P5+1) could be poised to reach a political understanding on a final Iran nuclear deal by March 31, if they are able to overcome two core issues still under discussion here.
They involve the scope of research and development that Iran could conduct in years 11-15 of a final accord, and what happens on UN Security Council sanctions, according to a senior US official.