US President Donald Trump has placed the Caribbean island under a de facto oil blockade, straining its ageing power grid.Cuba has reported its second nationwide blackout in less than a week, plunging the island into darkness shortly before evening.On Friday, the Union Electrica de Cuba, the state-owned utility in charge of the electrical grid, announced that the outage began at 4:30pm local time (20:30 GMT).Recommended Stories list of 3 itemsend of listNo explanation was given for the blackout. But it follows a similar power failure on Monday, bringing the total number of island-wide outages to four since the start of the year. Two other total blackouts struck in March.Outages are not uncommon in Cuba, where the electricity infrastructure is increasingly aged. Much of the system dates to the Cold War period, between 1960 and 1980.But the problem has intensified since January, when United States President Donald Trump effectively severed Cuba’s supply of foreign oil.Already, Cuba has been under the longest-running trade embargo in modern history. Since the 1960s, the US has largely barred trade with the island, which sits roughly 140 kilometres — or 90 miles — from its shores.Since taking office for a second term, though, Trump has sought to trigger regime change on the communist-led island. Critics have long accused the government in Havana of human rights abuses, including the violent suppression of dissent.On January 3, Trump authorised a military operation against Venezuelan President Nicolas Maduro, a socialist leader and ally of the Cuban government. The operation culminated in Maduro’s abduction and transport to New York, where he remains impr …