U.S. and Iran Want to Restore the Nuclear Deal. They Disagree Deeply on What That Means.

After five weeks of diplomatic shadow boxing, it is clear that the old agreement no longer works for Tehran or Washington, except as a steppingstone.

President Biden and Iran’s leaders say they share a common goal: They both want to re-enter the nuclear deal that President Donald J. Trump scrapped three years ago, restoring the bargain that Iran would keep sharp limits on its production of nuclear fuel in return for a lifting of sanctions that have choked its economy. But after five weeks of shadow boxing in Vienna hotel rooms — where the two sides pass notes through European intermediaries — it has become clear that the old deal, strictly defined, does not work for either of them anymore, at least in the long run. The Iranians are demanding that they be allowed to keep the advanced nuclear-fuel production equipment they installed after Mr. Trump abandoned the pact, and integration with the world financial system beyond what they achieved under the 2015 agreement.