Reuben Brigety, the US ambassador to the African country, is reportedly convinced that the country provided supplies to Russia, despite the country insisting that it remains neutral in the conflict in Ukraine.
Brigety said: "Among the things we noted was the docking of the cargo ship in the Simon's Town naval base between 6th to 8th December, 2022, which we are confident uploaded weapons and ammunition onto that vessel in Simon's Town as it made its way back to Russia."
"The arming of the Russians is extremely serious, and we do not consider this issue to be resolved, and we would like SA to [start] practising its non-alignment policy."
In January, Al Jazeera reported that South Africa was set to conduct military drills with Russia and China, which the US critized, fearing that it could have been a signal that South Africa was taking a side in the Ukrainian conflict.
The exercises, called Mosi, meaning "Smoke" in Tswana, one of South Africa's 11 official languages, saw 350 of the country's soldiers training alongside Russian and Chinese soldiers.
White House Press Secretary Karine Jean-Pierre said at the time: "The United States has concerns about any country … exercising with Russia as Russia wages a brutal war against Ukraine."
It is unclear how the Biden administration will respond to the recent revelation.
This is a breaking story and will be updated.