South Africa is formally protesting to the US ambassador over his allegations that it has sold arms to Russia.
Reuben Brigety alleged that a Russian ship was loaded with ammunition and weapons in Cape Town last December.
South Africa has said it has no record of an approved arms sale and President Cyril Ramaphosa has ordered an inquiry.
A cabinet minister has subsequently hit out at such “megaphone diplomacy”, saying South Africa could not be “bullied by the US”.
“It is the US which has sanctions against Russia… they must not drag us into their issues with Russia,” Khumbudzo Ntshavheni, the minister in the presidency, told public broadcaster SABC.
Her bullish comments follow a Kremlin statement saying President Vladmir Putin had spoken to his South African counterpart by phone and the two had agreed to deepen “mutually beneficial ties”.
But Pretoria has also sought to calm the diplomatic storm, which erupted after Mr Brigety’s news conference on Thursday, by saying it valued a “cordial, strong, and mutually beneficial” relationship with the US.
Officially, the department of international relations has said Foreign Minister Naledi Pandor will be speaking to her US counterpart Antony Blinken on Friday afternoon.
The US has provided no evidence of the accusations yet.
Earlier on Friday, White House spokesman John Kirby said the US had consistently urged countries not to provide support for Russia’s war in Ukraine, but he would not be drawn further over the affair except to say it was “serious issue”, Reuters news agency reports.
South Africa’s presidency told the BBC that details of its inquiry, to be chaired by a retired judge, would be provided in due course.
There is no dispute that a Russian ship, known as Lady R, docked at a naval base near Cape Town last December – prompting questions from local politicians at the time. Whether the ship was supplied with arms before returning to Russia still needs to be established.
But it is about more than a diplomatic row between old trade partners.
If the accusations are true, South Africa will have violated its own Arms Control Act, which commits to “not trade in conventional arms with states engaged in repression, aggression or terrorism”.
In the same act, South Africa describes itself as a “responsible member of the international community”.
The government said on Friday that it had no record of arms being sold to Russia, and that if this happened it was done covertly.
Even this possibility does not bode well for South Africa. At best it would speak to a government that does not have a handle on the country’s affairs and at worst would suggest complicity in Russia’s aggression against Ukraine.
South Africa is one of a handful of countries that has abstained from a number of UN votes on the conflict and has refused to publicly condemn Russia, insisting it is non-aligned on the matter.
For months the regional superpower has been saying it instead supports a mediated settlement to the conflict.
Supplying arms while claiming to be neutral would not only rubbish that stance but would leave South Africa with a lot to answer both to its citizens and the international community.
Some in the governing African National Congress (ANC) appear to have a lingering affection for Russia because of the then-USSR’s support for their fight against white-minority rule. But in present-day South Africa, many have been asking questions about whether this love affair truly serves South Africa’s interests.
Experts say the country has more in common and a much bigger trade relationship with the West. Some are worried about the possible economic impact if US ties strain further.
The country’s currency, the rand, which has been struggling for weeks as a result of months of rolling power cuts, weakened even further following the US ambassador’s accusations.
It is an additional problem that South African citizens can scarcely afford.
