Rain and bad light loom as Australia's main threats to a series-clinching victory, with South Africa 29-0 in its second innings after an abbreviated fourth day of the second Test at Kingsmead in Durban.
Fading light ended play 2.1 overs after tea, and the forecast is for more gloomy weather on day five, with the Proteas still trailing by 380, having been set the improbable target of 410 to square the three-Test series at 1-1.
Ricky Ponting closed Australia's second innings at 307-4, leaving South Africa to bat for five overs before tea, after he and Matthew Hayden scored centuries while putting on 201 in 56 overs for the second wicket. Adam Gilchrist plundered 22 off the second-last over of the innings - from Andre Nel.
Ponting, who complemented his gritty 225-ball 103 in the first innings with a commanding 187-ball 116, joined Indian legend Sunil Gavaskar as the only scorers of a hundred in each innings of three Tests.
Ponting was on 48 and Hayden 35 when they resumed at 125-1 - a lead of 227 - and they were not separated until the 36th over of the day when Hayden edged a drive off Makhaya Ntini to wicketkeeper Mark Boucher.
Hayden's handsome, controlled 102, with 12 fours off 217 balls, was his 26th century in 81 Tests, including his sixth in 15 Tests against South Africa.
Ponting left soon after Hayden, lofting Shaun Pollock high to deep square leg where Nicky Boje took the catch. The Australian captain sprinkled two sixes and 12 fours into his 30th century in 102 Tests, including his seventh in 14 Tests against South Africa.
While Damien Martyn's unbeaten 15 came off 37 balls, Gilchrist blasted 24 off eight balls before he was caught off the ninth, at long-on by Nel off left-arm spinner Boje - and Ponting declared immediately.
In the previous over, Gilchrist cover drove Nel for four, mishit the second ball to cover for two and pounded the next four balls to the boundary - to long-off, behind square leg (twice) and through extra cover.
Nel sledged Gilchrist at the end of the over and the Australian vice-captain responded quickly, telling the taunting fast bowler to 'show some respect'.
Ponting's previous hundreds in each innings of a Test this summer were 149 and 104no against the West Indies at the Gabba in November and 120 and 143no against South Africa at the SCG in January - his 100th Test.