By Daniel Trotta HAVANA, March 21 (Reuters) - Cuba's national electric grid collapsed on Saturday for the second time in a week amid the U.S.-imposed oil blockade, officials announced, as the communist government struggles to keep the lights on for its 10 million people with decrepit infrastructure.

Cuba’s electricity grid suffered another blackout on Saturday, the second major hit to its energy system this week, amid the US administration fuel embargo and pressure on the Havana government.