South Africa's foreign ministry said on Friday the US ambassador to South Africa, Reuben Brigety, had "admitted that he crossed a line" and "apologised unreservedly" following his allegations that the African country supplied weapons and ammunitions to Russia last year.
Reuben Brigety was summoned on Friday to the foreign ministry in a diplomatic uproar that has seen South Africa defend its "cordial, strong, and mutually beneficial" relationship with the US.
He met South Africa's Foreign Minister Naledi Pandor where he made the apology, the foreign ministry said in a statement.
"We conveyed our displeasure with his conduct and he admitted that he crossed the line and apologised unreservedly," spokesman Clayson Monyela said.
The foreign minister also held talks with her US counterpart Antony Blinken, he added.
"There's a commitment to use established diplomatic channels to raise whatever issue may arise in the management of the bilateral relations between the two countries," his statement said.
Earlier, a cabinet minister said South Africa could not be "bullied by the US", in an interview with public broadcaster SABC.
"They must not drag us into their issues with Russia," said Khumbudzo Ntshavheni, the minister in the presidency.
A statement on Kremlin website said President Vladimir Putin had a telephone conversation with South Africa's President Cyril Ramaphosa and they agreed "to further step up mutually beneficial ties".
President Ramaphosa had on Thursday said an investigation led by a retired judge was under way into the claims of weapons sale.
