Cuban Foreign Minister Bruno Rodriguez held talks with his Russian counterpart Sergey Lavrov and was set to meet later in the day with President Vladimir Putin.
Lavrov urged the U.S. to refrain from blockading Cuba, which has struggled to import oil for its power plants and refineries after U.S. President Donald Trump threatened any nation that sold oil to Cuba with tariffs.
"Together with most members of the global community, we are calling on the U.S. to show common sense, take a responsible approach and refrain from its plans of sea blockade," Lavrov said during the talks with Rodriguez.
He promised that Moscow will "continue supporting Cuba and its people in protecting the country's sovereignty and security."
Kremlin spokesman Dmitry Peskov also noted that "Russia, like many other countries, has consistently spoken against the blockade of the island."
"We have our relations with Cuba, and we value these relations very much," Peskov told reporters. "And we intend to further develop them — of course, during difficult times, by providing appropriate assistance to our friends."
Asked whether sending fuel to Cuba could derail a recent warming of ties with Washington, Peskov responded that "we don't think these issues are linked."
Putin has praised Trump's efforts to mediate an end to the conflict in Ukraine, and Moscow and Washington have discussed ways to revive their economic ties.
Venezuela, one of Cuba's main oil suppliers, stopped selling crude to the island in January after the U.S. captured then-President Nicolás Maduro in a pre-dawn raid and flew him to New York to face drug trafficking charges.
Mexico also cut off oil shipments to Cuba in January, after Trump issued the tariff threat.
Russia's Izvestia news outlet last week cited the Russian embassy in Havana as saying that Moscow was preparing to send humanitarian fuel shipment to Havana in the near future. On Monday, Russian ambassador to Cuba, Viktor Koronelli, said that Moscow was looking into details of organizing assistance to Cuba but offered no specifics.
Cuba's fuel shortages already have forced Russian tourist companies to halt the sales of package tours to the island after the Cuban government said that it will not provide fuel to planes that land on the island.