A Russian tanker carrying oil to Cuba has entered the waters off the Communist-run island, Russia's Interfax news agency reports.
The oil shipment - the first to reach Cuba since January - comes hours after US President Donald Trump said that he had no problem with countries, including Russia, sending supplies to the island.
Trump's remark appeared to signal a loosening of a de facto oil blockade his administration had imposed on Cuba since January.
Cuba has been experiencing a series of nation-wide blackouts as the blockade exacerbated existing shortages.
According to Interfax, the Russian tanker Anatoly Kolodkin is carrying a humanitarian shipment of 100,000 tonnes of crude oil.
Last week, the World Health Organization (WHO) had warned that severe fuel shortages meant that Cuban hospitals were struggling to maintain emergency and intensive care services.
Cuba's situation has deteriorated rapidly since January 3, when US forces seized Venezuelan leader Nicolás Maduro - a staunch ally of the Cuban government - who had been providing the island with oil under highly preferential terms.
Trump also threatened to impose tariffs on any nation sending oil to Cuba, but in an apparent reversal of his strategy, he told journalists on Air Force One that he had no problem with Russia delivering oil to Cuba.
The Russian tanker is expected to offload the oil in Matanzas terminal in the coming hours, providing Cuba with a much-needed lifeline as its Communist government negotiates with the Trump administration on potential solutions to the crisis.
Both sides have publicly set out a number of political and economic red lines, complicating the search for common ground. The Cuban leadership remains firm in its refusal to accept enforced changes to its government.
This situation is compounded by Cuba's pre-existing challenges, including a severe economic downturn exacerbated by the pandemic and the ongoing fuel blockade.
