South Africa was 55 for two in their second innings, a lead of 241, at lunch on the fifth and final day of the first Test against England at Edgbaston here on Monday.
England earlier strengthened their chances of holding on for a draw by avoiding the follow-on.
At lunch South Africa captain Graeme Smith was 37 not out and Boeta Dippenaar seven not out with a minimum of 78 overs left in the match.
Smith, who made a South Africa Test record 277 in the first innings, should have been stumped on 35 by Alec Stewart off left-arm spinner Ashley Giles but the 40-year-old wicketkeeper missed the chance.
South Africa first lost Herschelle Gibbs, who made 179 first time around, when the opener was bowled off his arm for nine by fast bowler James Anderson.
And then 30 for one became 32 for two when paceman Stephen Harmison, from around the wicket, had Gary Kirsten out for one when the left-hander fended a rising delivery straight to Anthony McGrath at short leg.
England started the final day on 274 for seven, 21 runs short of the follow-on target of 395.
Giles was nine not out and new batsman Darren Gough yet to face after Andrew Flintoff (40) was leg before wicket to fast bowler Dewald Pretorius off Sunday’s last ball.
Giles scored all 21 runs England needed to make South Africa bat again, including a purple patch of five boundaries in eight balls. Gough hung around for an 18-ball one when he mishooked Ntini to Jacques Rudolph at square leg.
Then, two balls later, Harmison was bowled for nought by Ntini, the ball just clipping his off-bail, to leave England 398 for nine.
Giles, who bats right-handed, was in sight of his third Test 50 in three matches, when he was bowled for 41 by former Warwickshire team-mate Shaun Pollock.
Giles faced 83 balls including eight fours. Anderson was nought not out.
England was all out for 408, a first innings deficit of 186, but crucially, they had made South Africa bat again.
Ntini finished with four for 114 while Pretorius took a Test-best four for 115 in his second match at this level. – Sapa-AFP