Negotiations to revive the nuclear deal with Iran are “in the final stretch,” the United States said this week. The Biden administration has urged Tehran to roll back its recent nuclear advances and make “tough political decisions” that would allow both countries to return to the 2015 pact.

But even as the two sides potentially prepare to thrash out everything from U.S. sanctions to Iran’s uranium enrichment, at least one key issue has been left off the nuclear negotiating table: the fate of four U.S. citizens being held in Iran.