|Second Test, Adelaide (day four):|
|Australia 550 & 267-8 dec v South Africa 388 & 77-4|
Australia need six South Africa wickets on the final day to win the second Test in Adelaide and take a 1-0 series lead.
Set what would be a Test record 430 for victory, the Proteas slumped to 77-4 by the close of day four as Nathan Lyon claimed two wickets.
Earlier, Australia converted their overnight 111-5 into 267-8 declared thanks to Mike Hussey's 54.
Australia will replace South Africa at the top of the world Test rankings if they win the three-match series.
Hussey and captain Michael Clarke played cautiously early on before upping the tempo with a driven boundary apiece off Rory Kleinveldt before the latter smashed 13 off one Imran Tahir over.
But Clarke (38) was out lbw to Dale Steyn in the next over and Hussey, who added a quick 33 with Matthew Wade, followed in the over before lunch, caught by Steyn when attempting a pull shot off Morne Morkel.
James Pattinson, who has been ruled out of the rest of the Test series with a rib injury, hit six boundaries in his 29 out out as he put on 47 with Ben Hilfenhaus (18 not out) before Australia declared.
South Africa's run chase got off to the worst possible start when captain Graeme Smith edged Hilfenhaus to Ricky Ponting at slip to depart for a duck in the first over.
Spinner Lyon then had Hashim Amla (17) caught by Clarke at slip and Jacques Rudolph (3) snapped up by Ed Cowan at short leg as the tourists stumbled to 45-3.
That became 45-4 when Peter Siddle bowled Peterson off his inside edge.
AB de Villiers and Faf du Plessis scored just 10 runs in the final hour as they finished on 12 not out from 101 balls, and 19 from 74 respectively as South Africa crawled to 77-4.