A Russian oil tanker under U.S. sanctions is set to arrive in Cuba carrying about 730,000 barrels of crude, challenging an American fuel blockade.

Cuba is facing a severe energy crisis after losing key oil supplies, leading to shortages and frequent blackouts.

The U.S. has warned against countries supplying oil to Cuba, but experts say it is now unlikely the tanker will be stopped.

Once refined, the shipment could briefly ease fuel shortages, especially diesel, Barron’s has reported.

Cuban officials must decide whether to use the fuel for electricity generation or to support transportation and the economy.