Sehwag took just 36 balls to score his half-century with the help of eleven boundaries. The right-hander added fifty-run stand with veteran Rahul Dravid to resurrect the run chase after losing Gautam Gambhir (3) early.
India started poorly as they lost opener Gambhir inside five overs. Pacer Ryan Harris struck early in 4.3 overs to dismiss Gambhir cheaply and reduce India to 14/1.
Earlier, Australia declared their second innings soon after the play resume in the post-lunch session and set 500 runs target for India with less than five sessions left in the match.
Ricky Ponting (60) and Brad Haddin (11) took Australia's overall lead to 499 runs when skipper Michael Clarke declare their innings close. Australia scored 167/5 in 46 overs in their second innings of the match after they declared their first essay at 604/7 on Day 2.
Australia lost Clarke (37) and Michael Hussey (15) in quick succession in the morning session of the fourth day of the fourth Test on Friday.
The hosts were 154/5 at lunch in their second innings with an overall lead of 486 runs with Ponting and Haddin at the crease.
Ishant Sharma trapped Hussey to give India second breakthrough. Umpire Dharmasena took his time before giving Hussey, who wasn't happy with the decision, marching orders. Australia lost their fifth wicket at the score of 147.
Ricky Ponting, who added 71 runs for the fourth wicket with Michael Clarke, hit another fine half-century to take Australia's overall lead past 475-run mark. Ponting's 50 came off in 73 balls and included four boundaries.
Seamer Umesh Yadav got rid of Clarke, who scored 43-ball 37 with the help of four boundaries. Australia lost their fourth wicket at the score of 111.
Yadav's full-length delivery got a faint outside edge from Clarke's bat en-route to wicketkeeper Wriddhiman Saha's hands.
Ponting hit two successive boundaries off Ishant Sharma to bring up 500 runs for the series and also take Australia's overall lead past 400-run mark against India. .
Clarke and Ponting resumed Australia's second innings on Day 4 after India conceded a huge first innings lead of 332 runs after the end of third day's play at the Adelaide Oval.
Australia resumed Day 4 at 50/3 in the second innings enjoying an overall lead of 382 runs.
There was some artificial excitement towards the end of third day's play when the home team lost their top-three for just 50 runs, but with an overall lead of 382 and seven wickets standing, Australia were merely stirred, not shaken.
Barring a miracle, it is hard to see this Indian line-up denying Australia a clean sweep of the four-Test series that was lost 10 days ago in Perth.
Virat Kohli provided the only bright moment by cracking his maiden century but India were still faced with a herculean task of preventing a 'whitewash' against Australia in the fourth and final Test.
Kohli stood bravely amidst the ruins with a gritty 116 but most of the other top batsmen surrendered meekly as India folded up for 272 in the first innings, and even though they were 332 runs in arrears of Australia's first innings tally - and therefore liable to follow-on - skipper Michael Clarke decided not to enforce the same.
Credit should also be given to young Wriddhiman Saha (35) who helped Kohli add 114 runs for the sixth wicket which helped the Delhi lad push for his three-figure mark. Kohli's delightful knock contained 11 boundaries and a six over deep mid-wicket off Michael Clarke's bowling.
The second new-ball again did the trick for Australia as India who were 225/5 at one stage lost five wickets for 47 runs in little over 10 overs.
Aussie paceman Peter Siddle charged in on the unresponsive flat Adelaide pitch to take five for 49, denting a few more Indian batting reputations and prolonging Sachin Tendulkar's wait for a 100th international century.
