Usman Khawaja and captain Steve Smith led the charge for Australia after the loss of two early wickets on the second day of the day-night third Test against South Africa on Friday.

At tea in Adelaide, the Australians were 109 for two in reply to the Proteas' 259 for nine declared, with Khawaja unbeaten on 58 and skipper Smith not out 23. The home side trail by 150 runs.

Khawaja, who has been Australia's most consistent batsman in a troubled series, was the rock of the home team's fightback.

He occupied the crease and stalled the Proteas' momentum after they got the wickets of Matt Renshaw and David Warner inside the first hour.

Khawaja reached his third half-century of the series, off 115 balls, with successive boundaries off Kyle Abbott nearing the adjournment.

The wristy left-hander has scored 227 runs for the series up to tea and with Smith put on 72 runs for the unbeaten third wicket.

Renshaw, who looked so composed in his first Test innings the previous evening, fell to a superb sprawling catch by Dean Elgar in the slips for 10 in the fourth over of the day.

Abbott enticed an edge and Elgar dived across second slip to take the catch just above the ground and send the English-born youngster on his way.

Abbott, bowling at a nagging length, prised the key wicket of Warner for 11 in his eighth over, nipping one off the wicket and getting the Australian vice-captain to edge to Elgar for his second catch.

Warner, who was unable to open the innings because of the time he spent off the field having treatment when South Africa made a daring declaration late on the first day, came in at number three.

Abbott gave little away and in the first hour had the impressive figures of two for seven off his unchanged seven-over spell.

Australia, well beaten in the first two Tests, are battling to avoid their first-ever home Test series whitewash, as well as their sixth straight defeat.