US Secretary of State Antony Blinken has arrived in South Africa at the start of a three-nation African tour aimed at countering Russia's efforts to boost its influence.
Last month Russia's Foreign Minister Sergei Lavrov visited four African countries as he tried to gain support for the war in Ukraine.
South Africa has remained neutral in the Ukraine war, refusing to join Western calls to condemn Moscow.
After Pretoria Mr Blinken will visit the Democratic Republic of Congo and Rwanda.
Tensions between the neighbouring countries have flared in recent months amid an escalation of conflict in eastern Congo.
