Cuba hit out at the United States on Thursday over a "campaign of discredit and lies" against the doctors it has sent around the world to help fight the coronavirus pandemic.
Following requests in recent weeks, communist Cuba has sent medical teams to Italy, Venezuela, Nicaragua, Grenada, Suriname, Jamaica and Belize.
The export of medical services is one of the pillars of the Cuban economy that has suffered almost six decades of crippling US sanctions, bringing in $6.3 billion in 2018, according to official figures.
"The American government's campaign of discredit is immoral in any circumstances, and it's particularly offensive for Cuba and the world in times of a pandemic that threatens all of us," said the foreign ministry.
The US State Department is waging "a continuous and exacerbated campaign of discredit and lies against the international medical cooperation supplied by Cuba," the ministry said in a diplomatic protest statement.
"#Cuba offers its international medical missions to those afflicted with #COVID-19 only to make up the money it lost when countries stopped participating in the abusive program," said the State Department on Twitter.
Cuba, which is world renown for its medical training program, has more than 30,000 doctors working in 61 countries.
However, following governmental swings from leftist allies to right-wing opponents, several countries -- including Brazil, Bolivia, Ecuador and El Salvador -- sent the doctors home to Cuba.
The State Department said the Cuban state, which provides free education, "keeps most of the salary its doctors and nurses earn while serving in its international medical missions while exposing them to egregious labor conditions."
"Host countries seeking Cuba's help for #COVID-19 should scrutinize agreements and end labor abuses."
Cuba says it pays its medical professionals enough money to cover their expenses in their host country, on top of a salary of around $50 a month paid in Cuba.
The rest of the money made from the program helps ensure health and education remain free for everyone on the Caribbean island nation, Havana says.