HAVANA -- Cuban officials say a shipment of coronavirus aid from Asia's richest man, Jack Ma, has been blocked by the six-decade U.S. embargo on the island.

Carlos M. Pereira, Cuba's ambassador to China, said on his blog this week that Ma's foundation tried to send Cuba 100,000 facemasks and 10 COVID-19 diagnostic kits last month, along with other aid including ventilators and gloves.

Cuba was one of 24 countries in the region meant to receive the donations announced on March. 21 by the Jack Ma Foundation, which is sending similar aid to countries around the world, including the United States.

Cuban officials say the cargo carrier of Colombia-based Avianca Airlines declined to carry the aid to Cuba because its major shareholder is a U.S.-based company subject to the trade embargo on Cuba. The embargo has exceptions for food and medical aid but companies are often afraid to carry out related financing or transportation due to the risk of fines or prosecution under the embargo.

Human-rights groups have been calling for the U.S. to lift sanctions on Venezuela, Cuba and Iran during the coronavirus epidemic in order to permit the flow of more aid. The Trump administration has argued that only the countries' government would benefit from the sanctions relief.

An Avianca spokeswoman referred a query to a spokeswoman for Ma's company, Alibaba, who did not return an email seeking comment.

Cuba has closed all air and sea connections, with the exception of essential cargo and government flights, in an attempt to prevent the further introduction of coronavirus to the island.As of Friday morning, Cuba had 269 confirmed cases, 3,241 people in quarantine, 15 patients recovered from the infection and six who have died of it.

A town in western Cuba and a relatively well-off section of Havana have both been completely isolated to prevent the spread of the disease.

Cuba has free universal health care and a high ratio of medical workers, 95,000, for a population of 11 million but operates without much of the equipment and testing generally available in developed countries.

The blocking of the aid should be “an action inconceivable in a global crisis,” but “it doesn't surprise us,” said Carlos Fernando de Cossio, Cuba's head of U.S. affairs. “It's the type of obstacle that Cuba confronts daily in order to take care of the country's basic necessities.”