President Trump on Thursday signed an executive order that would impose a tariff on any goods from countries that sell or provide oil to Cuba, a move that could further cripple an island plagued by a deepening energy crisis. This week has been marked by speculation that Mexico would slash oil shipments to Cuba under mounting pressure by Mr. Trump to distance itself from the Cuban government. YAMIL LAGE /AFP via Getty ImagesSince the Venezuela operation, Mr. Trump has said that no more Venezuelan oil will go to Cuba and that the Cuban government is "ready to fall." On Jan. 11, Mr. Trump wrote on social media that "there will be no more oil or money going to Cuba — zero." It remains unclear what the Thursday order by Mr. Trump will mean for Cuba, which has been roiled by crisis for years and a U.S. embargo.