South Africa says it is sending more soldiers to support government forces in the Central African Republic, where rebels are threatening the capital.
An estimated 200 South African troops are already in the CAR to train army personnel, under a defence agreement.
South African Jacob Zuma's office said 400 troops would be deployed in total.
The Sekela rebels - who have halted their offensive on the CAR capital Bangui - are due to hold talks with the government in the coming days.
A foreign ministry spokesman in Pretoria said the additional troops would protect members of the South African military already training government forces in the CAR.
The statement from Mr Zuma's office said the deployment was part of South Africa's efforts "to bring about peace and stability in the region".
Several countries in the region - Gabon, the Republic of Congo, Chad and Cameroon - have troops there as part of the Central African Multinational Force (Fomac).
Since the Seleka rebels began their campaign last month ago, they have taken several key towns and cities, including the diamond centre of Bria and Sibut.
But CAR and international forces are holding the strategic town of Damara, about 80km (50 miles) north of Bangui.
It is the biggest threat President Francois Bozize has faced since he took power in a coup in 2003.
Both the US and France, the former colonial power, have rejected a plea by the government for help to defeat the rebels.
Seleka - an alliance of three rebel groups - accuses the government of failing to honour a 2007 peace deal under which fighters who laid down their arms were meant to be paid.
They have dismissed the president's offer to form a national unity government.