The US government says it will stop funding programmes in South Africa intended to tackle the spread of HIV and Aids, linking the decision to the government's alleged failure to protect the white-minority Afrikaner community.
South Africa's health ministry responded by saying that though it had not been informed of this decision, it had "long been working on a self-reliance plan".
More than eight million South Africans are living with HIV – the highest number of any country in the world.
Until 2025, the US was supporting South Africa's efforts to deal with the virus with an estimated $400m (£300m) a year through the President's Emergency Fund for Aids Relief (Pepfar).
But since the inauguration of President Donald Trump, relations between the two countries have increasingly soured.
Shortly after he came into office, Trump issued an executive order alleging that "countless" South African policies dismantled equal opportunities and fuelled violence "against racially disfavored landowners".
This is disputed by the South African government, which says its Black Economic Empowerment policy is needed to correct economic inequality dating from the apartheid era.
The executive order also highlighted South Africa's case against Israel at the International Court of Justice and its links to Iran.
The White House said that given these "unjust and immoral practices", further aid to South Africa would not be provided.
Trump has also falsely alleged that there is a "white genocide" taking place in South Africa, which has led to the administration setting up a refugee programme for Afrikaners - descendants of western Europeans who settled in southern Africa in the 17th Century. They are now just about the only refugees being allowed into the US.
Pepfar funding, which had been providing about a fifth of South Africa's total spending on HIV programmes, got a reprieve last October with what was called a "bridge plan".
But a US State Department official has confirmed that a "phased drawdown" of Pepfar funding would now start.
This was because of "South Africa's failure to make demonstrable progress on policy requests by the administration", the official said.
The intention of the US government was to "foster self-reliance" and reduce dependency on American funding, they added, pointing out that "South Africa is a middle-income country and is more than capable of supporting its own health programs".
South Africa's health ministry has said that while Pepfar contributed to the country's HIV programme, the provision of life-saving antiretroviral drugs was funded entirely separately, with most coming from the government.
Attempts to mend US-South Africa relations have floundered. These include a high-profile White House meeting between Trump and South African President Cyril Rampahosa just over a year ago when the US president confronted his counterpart with his claims of white persecution.
The US also boycotted the G20 meeting, a gathering of the world's major economies, hosted by South Africa last November.
Additional reporting by Pumza Fihlani in Johannesburg
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