NEW YORK (Thomson Reuters Foundation) - United States officials on Thursday called on all nations to stop using Cuba’s medical missions, which send doctors around the world, saying that Cuba refused to pay the medical staff and held them against their will.

Cuba’s international medical missions are a form of human trafficking and modern slavery, U.S. State Department officials told a news conference in New York.

The Caribbean island nation has a respected health service and generates major export earnings by sending more than 50,000 health workers to more than 60 countries.

But it came under criticism in Brazil, where President Jair Bolsonaro last year called the Cuban doctors “slave labor” and Cuba recalled its 8,300 medical workers stationed there.

Ramona Matos, a Cuban doctor, said she worked with medical missions in Bolivia and Brazil where Cuban security agents took away the doctors’ passports and other identification.

“We were undocumented,” she said at the State Department’s news conference. “If anything happened to us, we got hurt, we died ... nobody would know our identity.”

Nearly all of the doctors’ earnings were sent back to Cuba where they were frozen in accounts that they could not access until they completed their missions, she said.

“We were basically being trafficked, and we were victims and exploited by the Cuban government,” she said.

The United States and Cuba have had a strained relationship since Fidel Castro took over in a 1959 revolution, and a U.S. trade embargo has been in place for decades.

The State Department is analyzing where Cuban missions are practicing, which is in at least 66 countries, said Deputy Assistant Secretary of State for Cuba Carrie Filipetti.

The U.S. government also is publicizing its criticisms of the Cuban medical missions so that host countries “can’t say they weren’t aware that this was human trafficking,” she said.

Nations where the Cuban medical missions are working need to end the practice, said Carlos Trujillo, U.S. ambassador to the Organization of American States.

“Across the Americas, there are multiple countries that continue to have these programs,” he said.

“What we’re really asking here is for a lot of the countries ... who are continuing to traffick and conduct these type of activities with Cuban doctors in their countries to please stop.”

Several doctors who were part of Cuba’s program but left filed a federal lawsuit in Florida last year against the Pan American Health Organization (PAHO), an international agency that brokered Cuba’s arrangement with Brazil.

The doctors said PAHO, a division of the World Health Organization, was enabling the trafficking of medical professionals.