A top U.S. State Department official resigned this week after President Donald Trump announced the United States is withdrawing from the Iran nuclear deal, according to a report in the journal Foreign Policy.

The report says 38-year-old nuclear proliferation expert Richard Johnson resigned his position as acting assistant coordinator in the State Department's Office of Iran Nuclear Implementation, which had been involved in talks with Britain, France, Germany and other nations to salvage the deal that rewarded Iran for giving up much of its nuclear activities in trade for relief from economic sanctions.

Trump announced Wednesday that the U.S. would no longer be part of that deal. Johnson's farewell party was held that night, according to Foreign Policy.

Johnson did not make a statement to the journal for its report, but Foreign Policy reports that his farewell email to colleagues and staff praised the deal, calling it an "extraordinary achievement" and saying it has "clearly been successful in preventing Iran from acquiring a nuclear weapon."

Johnson's departure highlights the Trump administration's loss of high-level career diplomats at the State Department and across the breadth of the federal government. The report notes that the office Johnson headed has gone from a full-time staff of seven to none since Trump's inauguration.

That development was due in part to former Secretary of State Rex Tillerson's decision to close the department's office in charge of coordinating sanctions and move some experts to administrative roles.

Several former government employees contacted for the story, including former U.S. Treasury official Brian O'Toole, told Foreign Policy that they are dismayed at Johnson's departure. O'Toole called the nonproliferation expert "exactly the kind of person we want to keep in government."

O'Toole added, "You can't be powerful without good people in government."

Contacted for comment on the story, the State Department said in a statement that it does not comment on matters involving individual employees. But it added: "As directed by the President, we will continue to work with nations around the world to create a new coalition to counter Iran's nuclear and proliferation threats, as well as its support for terrorism, militancy, and asymmetric weapons like ballistic missiles."