A newly drafted United States nuclear strategy that has been sent to President Trump for approval would permit the use of nuclear weapons to respond to a wide range of devastating but non-nuclear attacks on American infrastructure, including what current and former government officials described as the most crippling kind of cyberattacks.

Iran’s top nuclear negotiator was heading back to Tehran on Sunday to consult with his nation’s leadership, as negotiators remained divided over how to limit and monitor Tehran’s nuclear program and even on how to interpret the preliminary agreement they reached two months ago.

Five former members of President Obama’s inner circle of Iran advisers have written an open letter expressing concern that a pending accord to stem Iran’s nuclear program “may fall short of meeting the administration’s own standard of a ‘good’ agreement” and laying out a series of minimum requirements that Iran must agree to in coming days for them to support a final deal.

David Sanger, senior fellow at the Belfer Center and adjunct lecturer in public policy at Harvard Kennedy School, was interviewed on NPR’s “On Point” about his new book on President Obama’s foreign policy efforts, including a cybercampaign against Iran’s nuclear program. Sanger’s book, Confront and Conceal: Obama’s Secret Wars and Surprising Use of American Power, was published this week.