The US Secretary of State Mike Pompeo has criticised South Africa for accepting more than 200 Cuban medics to help battle the virus.
Mr Pompeo accused Cuba of profiting from the pandemic, the AFP news agency reports.
"We applaud leaders in Brazil and in Ecuador and Bolivia and other countries which have refused to turn a blind eye to these abuses by the Cuban regime," Mr Pompeo said.
"And [we] ask all countries to do the same, including places like South Africa and Qatar."
The team of Cuban medics arrived in the African nation on Sunday night.
They include family physicians, epidemiologists, biotechnology experts and health-care technology engineers.
Cuban President Miguel Diaz-Canel reacted to Mr Pompeo by tweeting: "The United States lie deliberately when they attack Cuba's international medical cooperation with lies and slanders."
So far, South Africa has 3,174 active Covid-19 cases with 2,073 patients already recovered. To date, the country has a total of 5,350 cases with 103 deaths.
South Africa is one of the worst-hit African countries by Covid-19 alongside Egypt, Morocco and Algeria.