US prosecutors are preparing to unveil drug trafficking charges against the head of Venezuela's National Guard, according to people familiar with the case, as the United States investigates the suspected involvement of senior Venezuelan officials in the cocaine trade.

Nestor Reverol, the former head of Venezuela's anti-narcotics agency, is named in a sealed indictment pending in federal court in New York, according to the people.

He would be one of the highest-ranking Venezuelan officials - and the only one currently in office - to face US drug charges.