WASHINGTON — The Food and Drug Administration is implementing a new hiring protocol that could make it significantly harder for foreign scientists to find jobs and research opportunities at the agency, according to interviews and newly obtained documents.

The FDA recently began directing hiring managers not to extend any employment offers — including for fellowship and contractor positions — to any individual who has not lived in the U.S. for at least three of the five previous years, according to briefing materials shared with STAT that have been presented to some agency employees.