The South African cricketers are 229 for three, a lead of 199 runs after three days of the second Test against Australia at the Wanderers in Johannesburg.
The home side was 90 for three at one stage, before Hashim Amla and AB de Villiers seized control with an unbeaten 139-run stand.
Amla is on 89 and de Villiers 70.
Australia need to win to square the two-Test series, however history is against them, with only four teams having ever won in Johannesburg batting last.
The record fourth innings run chase at The Wanderers ground is 294 set by Australia in 2006 and unless the tourists can roll South Africa quickly on day four, their struggling top order faces a record pursuit on a fourth and fifth day pitch.