The US ambassador to South Africa on Thursday accused the country of supplying arms to Russia.
Reuben Brigety said weapons and ammunition had been loaded on to a Russian freighter docked in Cape Town last December.
“We are confident that weapons were loaded on to that vessel and I would bet my life on the accuracy of that assertion,” Mr Brigety told South African media.
He added that the situation was “fundamentally unacceptable” and an “inexplicable” deviation from South Africa’s policy of non-alignment.
The remarks chafed Pretoria and President Cyril Ramaphosa’s office hit back.
The comments “undermine the spirit of co-operation and partnership” between the two nations, said Vincent Magwenya, a spokesman for Mr Ramaphosa.
The US State Department took a more nuanced approach than its representative in South Africa.
“The US has serious concerns about the docking of a sanctioned Russian cargo vessel at a South African naval port in December of last year,” said State Department spokesman Vedant Patel.
“And as good partners do, we have raised those concerns directly with multiple South African officials.”
South Africa has professed a desire to remain neutral on the Russian invasion of Ukraine and abstained from voting on UN resolution condemning the attack last year.
Agence France-Presse contributed to this report
