The signers cover a range of prominent diplomatic and military figures, Democrat and Republican, spanning decades of foreign policy experience. They include Brent Scowcroft, a former national security adviser; Gen. Michael V. Hayden, former director of the National Security Agency and the Central Intelligence Agency; former Senators Richard G. Lugar and Sam Nunn; Adm. Eric T. Olson, former commander of Special Operations Forces; and Adm. William J. Fallon, former commander of the United States Central Command.
Former ambassadors who signed include Ryan C. Crocker, who served in Afghanistan, Iran, Pakistan, Syria, Kuwait and Lebanon; Daniel C. Kurtzer, who served in Israel and Egypt; James B. Cunningham, who served in the United Nations, Israel and Afghanistan; Thomas R. Pickering, a former under secretary of state who served in Israel, Russia, India, El Salvador, Nigeria, Jordan and the United Nations; and William C. Harrop, who served in Israel and as the State Department’s inspector general.
The release of their statement came less than two months before an American law requires Mr. Trump to decide whether to restore nuclear-related sanctions on Iran. He has suggested that he will restore them, which would effectively terminate the American pledge to heed the nuclear agreement’s provisions.
The 2015 agreement, negotiated under President Barack Obama, curtails Iran’s nuclear activities in exchange for eased economic sanctions. It provides for unprecedented international inspections of Iranian facilities to ensure compliance with Iran’s repeated vow that it will never develop a nuclear weapon.
Mr. Trump has criticized provisions of the agreement that expire after a number of years, arguing they should be permanent. He also has complained that the accord does not prohibit Iran’s ballistic missile activities.
His views have been welcomed by the governments of Israel and Saudi Arabia, which both see Iran as a regional menace, and in Israel’s view, an existential threat.
Britain, France and Germany, which signed the nuclear accord, agree with Mr. Trump’s concern about Iranian missiles, but say that issue should be discussed separately.
Iran has said it will not renegotiate the nuclear agreement.
The prospects that Mr. Trump will terminate American participation rose significantly in the past few weeks, when he dismissed his secretary of state and national security adviser, replacing them with loyalists who are outspoken in their antipathy toward Iran.
Mr. Trump’s new choices for secretary of state, the C.I.A. director Mike Pompeo, and for national security adviser, the former ambassador John R. Bolton, have both denounced the nuclear agreement.
Wendy R. Sherman, a former under secretary of state who was the lead American negotiator for the nuclear agreement, said in an Op-Ed essay published in The New York Times on Monday that Mr. Bolton’s elevation, in particular, “has only cemented the expectation that the nuclear deal’s life expectancy is short.”