U.S. officials said Sunday that negotiations between the United States and Iran have been slowed in part because Ayatollah Mojtaba Khamenei is operating from an extremely isolated location that has made communication inside the Iranian government difficult.

Iran’s supreme leader “is effectively holed up in an undisclosed location with little access to the outside world and is only reached by a labyrinth of couriers,” according to CBS News, which spoke with U.S. officials.