Prosecutors would lay out in detail for Flynn and his lawyers the fruits of their investigation into his activities. Prosecutors would also provide Flynn an opportunity to offer what’s called a proffer, detailing what information, if any, he has that could implicate others in wrongdoing.

Of interest to federal agents, according to people interviewed by the FBI, is his alleged role in a bizarre, unrealized proposal first reported by The Wall Street Journal to kidnap Turkish dissident cleric Fethullah Gulen, who is living in exile in rural Pennsylvania and is suspected of involvement in a failed coup attempt.