actual construction of an atomic bomb. does that mean that an israeli military strike on iran's nuclear facilities would be postponed? michael sing is the former senior director of middle eastern affairs at the national security council. michael, what is the specific meaning of this conclusion that the iranians on the u.s. have come to about iran and its nuclear ambitions? >> well, jon for a longtime now the u.s. conclusion has been that we don't have sufficient evidence to say definitively that iran is putting together a nuclear weapon. that is very different jon from saying that we have concluded that iran is not seeking a nuclear weapon. there are always intelligence gaps that make definitive conclusions difficult. if luke at iran's nuclear program and all the things they are doing there is really no other plausible conclusion is that they want to at least leave open the possibility of having a nuclear weapon stphaot fact that they have put so many of these facilities underground and hidden them from inspectors,