In the eyes of Mike Pompeo, the day was shaping up to be one of his most commanding displays of diplomacy since becoming secretary of state. Months of planning had finally yielded a meeting among reluctant European officials, Arab leaders and the Israeli prime minister to strategize over confronting Iran.

President Trump’s threat to rip up the Iran nuclear deal has touched off an urgent scramble in European capitals to preserve the agreement — not by rewriting it, but by creating a successor deal intended to halt Iran’s ballistic missile program and make permanent the restrictions on its ability to produce nuclear fuel.

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.