and vali nasr is from the john hopkins school for advanced international studies and a senior adviserthe state department under president department. vali, give us a sense of -- what is the state of play right now? why is it that what seems like something that could be very simple, joe biden said we'll be back in the iran deal because we thought it was a good way to keep iran contained and not developing nuclear companies, the iranians said if the u.s. comes back, we'll return to the deal. that seems like a fairly simple thing to happen, and here we are neither side is in the deal. >> well, first of all, joe biden did not go back to the deal very quickly. he essentially sat on trump sanctions and demanded that iran go into compliance first. the iranians saw this as additional u.s. pressure to get concessions from them and then they dug in by saying they're going to enrich further and perhaps escalate in the region. but the problematic is that the nuclear deal -- some aspects of it will expire during president biden's tenure of office, by 2023. and the united states is facing a dilemma