Oil Tanker
© Reuters / Desmond Boylan
US National Security Advisor John Bolton has put insurance and shipping companies that take part in the oil shipments from Venezuela to Cuba on notice.

"The Venezuelan National Assembly has decreed the suspension of crude exports to Cuba following the collapse of the national electrical grid. Insurance companies and flag carriers that facilitate these give-away shipments to Cuba are now on notice," Bolton tweeted.

Cuba is the closest regional ally of Venezuela and a major importer of its crude. The "on-notice" tweet is part of the latest escalation between Venezuelan and the United States after Washington slapped a fresh round of sanctions on PDVSA in January following Nicolas Maduro's inauguration for a second term as president.

Since then, Washington has increased the pressure by declaring its support for National Assembly President Juan Guaido. The declaration was followed by action. The US seized PDVSA assets in the United States and set up a new account where importers of Venezuelan crude in the US would transfer payments, to which only Guaido's camp would have access.

Despite these actions, Maduro has clung on to power with the help of Russia, which, along with China, Turkey, and Bolivia, has taken the stance that he is the elected president.

Meanwhile, Washington has turned to importers of Venezuelan crude, insisting that they stop buying it in a bid to cut off access to the market of Venezuela's virtually one and only export commodity right now. Most recently, US Secretary of State Mike Pompeo asked India to stop buying Venezuelan crude to stop being "the economic lifeline for the Maduro regime." India is Venezuela's second-largest oil buyer.