Having South African troops in the war-torn Central African Republic (CAR) could cost taxpayers more than R1.2-billion over five years, President Jacob Zuma said on Monday.

In a letter to National Assembly speaker Max Sisulu, Zuma clarified that his initial estimate of R65-million for the deployment of 400 South African National Defence Force (SANDF) members was only for the period January 3 to March 31.

"No provision has been made yet for the financial year 2013/14 for this employment," said Zuma.

His letter followed criticism by Democratic Alliance MP David Maynier, who questioned the amount the president had said would be spent on the deployment.

Zuma said that while no budgetary allocation had been made, the deployment of troops would run to March 31, 2018, in terms of a memorandum of understanding (MOU) between South Africa and the CAR.

"Therefore, this employment will run up to the end of the duration of our MOU, however if the situation improves in the intervening period, we will revise the protection element accordingly."

Zuma said the Treasury was being consulted on the additional funds needed for the deployment.

"The department of defence estimates that approximately R21-million per month would be required."

Maynier welcomed Zuma's clarification on Monday.

"He [Zuma] has effectively conceded that a mistake was made in estimating the cost of the employment," said Maynier.

He said he would write to the Joint Standing Committee on defence to have a special hearing on the deployment.

"We have to get to the bottom of why we are planning to sink R21-million per month – or R1.26-billion over five years – into the CAR," said Maynier.

Zuma signed off on the deployment in January so the SANDF could "assist with capacity building of the CAR defence force and assist the CAR with the planning and implementation of the disarmament, demobilisation and re-integration processes."