Iranian hard-liners have long mocked their foreign minister, Mohammad Javad Zarif, as the make-believe American, after a character in a comic Iranian movie who puts on an accent, wardrobe and lifestyle to live out a fantasy of American life.

A resident of the United States on and off for nearly 30 years, Mr. Zarif was the Iranian most closely associated with the negotiation of the 2015 deal that limited Iran’s nuclear program in exchange for relief from sweeping economic sanctions.

To ordinary Iranians and reformists, that made him a hero. To hard-liners, though, he was a dupe, seduced by the West into a deal that the Americans would never live up to.

Now, with the nuclear deal on the brink of collapse, with the Trump administration reimposing crushing sanctions on Iran, and with Tehran threatening to restart elements of its nuclear program, Mr. Zarif is coming under renewed fire not only from hard-liners in Tehran but also from Washington. White House officials say that President Trump has requested sanctions specifically against the Iranian foreign minister, stirring debate in both countries about the administration’s intentions.