Smith, who reached his half-century off 93 balls from the first ball after lunch, needed just another 58 deliveries to bring up his century.
However, the left-hander departed the next ball when his attempted pull shot off left-arm swing bowler Wahab Riaz.
Score Board
SOUTH AFRICA (I Innings):
Smith c Umar b Riaz 100
Petersen c Younus b Rehman 67
Amla c A Akmal b Riaz 80
Kallis (batting) 53
Harris (batting) 0
Extras (B-6, LB-2, W-1, NB-2) 11
Total (for 3 wkts, 89.3 overs) 311
Fall of wickets: 1-153, 2-190, 3-307.
Bowling: Gul 18.3-2-73-0, Riaz 18-3-61-2, Rehman 27-2-91-1, Ajmal 25-5-77-0, Hafeez 1-0-1-0.
(Published 12 November 2010, 16:03 IST)