Smith - an uncomplicated and powerful left-hander - made full use of the opportunity to bat first on a flat pitch, but was then run out on 99 as he attempted to reach three figures with a quick single.

Nevertheless, the 21-year-old left-hander, who had faced just 106 balls, hitting five fours and two sixes, had played a crucial hand in ensuring that Sri Lanka will have to chase a mammoth 318 run target.

Smith, playing in his 14th match, added 47 in 48 balls with Nicky Boje and then a record equaling 134 from 138 balls with Boeta Dippenaar for the third wicket.

Dippenaar, one of the middle order batsmen needing to cement his place for the World Cup, also played a fine hand, scoring a personal best 89 from 97 deliveries before sacrificing his wicket in the slog overs.

With Jacques Kallis smashing 53 from just 24 balls, the second fastest fifty by a South African, the home side posted their highest ever score against the Sri Lankans, surpassing the 311/9 scored at Lahore in 1997/98.

Sri Lankans had started the afternoon well after losing the toss, restricting the South African openers in the early overs, but Smith gradually wrestled away the initiative from the visitors.

Opener Herschelle Gibbs, who looked to be positive whenever possible, cracking three boundaries including one imperious pull shot, was clean bowled as he shuffled down the wicket and tried to loft Gunaratne over the top.

The right-hander had scored 16 from 25 balls and South Africa were 20 for one after 7.1 overs.

Left-hander Nicky Boje was promoted up the order to accelerate the scoring, a task he achieved, adding 47 runs in 48 balls with Graeme Smith.

But straight after the drinks break he perished as he top edged a paddle-pull off Dilhara Fernando. He has scored 28 from 34 balls, hitting four fours.

With the fielding restrictions having been lifted Sri Lankan captain Sanath Jayasuriya introduced his part-time spinners, rotating them quickly to try and upset the rhythm of the batsmen.

But Smith and Dippenaar milked the part-timers successfully and gradually lifted the run rate above five runs an over. Jayasuriya grew visibly frustrated as the Sri Lankan bowling and ground fielding deteriorated.

Between the 20th and 35th over the pair took full charge, scoring 105 runs. Despite the run out of Smith by Mahela Jayawardene in the 37th over, South Africa crashed another 129 runs in the final 15 overs.

To make matters worse the Sri Lankans were slow bowling their overs and were penalized one over by match referee G. Viswanath. In truth they could have been penalised even more considering that they had bowled just 46 overs by the scheduled close.

Earlier in the day, Sri Lanka had made two changes, including leg-spinning all-rounder Upul Chandana and medium pace all-rounder Hasantha Fernando in place of fast bowler Prabath Nissanka and Jehan Mubarak.

South Africa made one change, recalling middle order batsman Jonty Rhodes who had recovered from a hamstring injury.