Centrifuges. Sanctions. Nuclear research. Sticking points remain on some of the most basic points as the negotiations between world powers and Iran over Tehran's nuclear program hit crunch time.
Tuesday is the deadline for the two sides to finalize a framework agreement. That deal, if it can be reached, is supposed to be the basis for a final accord by the end of June detailing steps for Iran to scale back its uranium enrichment and other technology that could be used to make nuclear arms.