"The Ambassador’s remarks undermine the spirit of cooperation and partnership that characterised the recent engagements between US government officials and a South African official delegation led by National Security Special Advisor to the President Dr Sydney Mufumadi," the presidency said in a statement.
Earlier, the US ambassador to the country alleged that South Africa had loaded weapons onto a Russian ship, which docked at the Simon's Town naval base last December. President Cyril Ramaphosa answered a question by the National Assembly about the allegations, saying that the matter was "being looked into".
"It is public knowledge that a Russian vessel known as Lady R docked in South Africa. Allegations have since been made about the purpose of the voyage. While no evidence has been provided to date to support these allegations, the government has undertaken to institute an independent enquiry to be led by a retired judge," the presidency's statement reads.
According to the presidency, the Lady R matter was discussed in recent engagements between the South African and US representatives "and there was an agreement that an investigation will be allowed to run its course".
"It is therefore disappointing that the US Ambassador has adopted a counter-productive public posture that undermines the understanding reached on the matter and the very positive and constructive engagements between the two delegations."