By David Shepardson and Mark Hosenball
WASHINGTON (Reuters) - U.S. authorities are planning to ban passengers traveling on certain U.S.-bound foreign airline flights from carrying on larger electronic devices in response to an unspecified terrorism threat, a U.S. government official told Reuters.
The official said no American carriers are impacted by the ban, which would involve devices larger than a cell phone. The new rule is expected to be announced on Tuesday by the Homeland Security Department and cover about a dozen foreign carriers.
(Editing by Sandra Maler)