"Ideally we would like to bat once in this game, that will be goal No. 1," Smith said. "We will definitely bat the morning session tomorrow."
Smith plundered records in a superb display of chanceless batting. He drove leftarm spinner Zulfiqar Babar to midwicket and ran two runs to complete his first double century against Pakistan off 326 balls and also became the second South African after Kallis (13,140) to score more than 9,000 test runs.
Both Smith and De Villiers made batting look very easy on a dry wicket where Pakistan was bowled out for just 99 inside three hours on the first day.
"The goal for today was to get ourselves into a position from where we could win the game," Smith said. "The way AB played and transferred pressure, it made my life a lot easier, it was terrific knock from him."
Pakistan's plan to break the partnership by giving the second new ball to the spinners from one end after lunch went horribly wrong and both batsmen went on a run rampage by adding 139 runs in 26 overs in the second session before adding further 123 in 33 overs after tea.
Smith raised his 150 by hitting Ajmal for three successive boundaries while De Villiers completed his 17th test hundred in the last over before tea when he drove the offspinner to the cover fence.
Pakistan's lone wicket came early in the day when Steyn added six more to the team's overnight 128-3 before he offered no shot off lanky pacer Mohammad Irfan's delivery that knocked his exposed off stump.
And with the lead only 35 at that stage, Irfan should have had the wicket of De Villiers next ball, but wicketkeeper Adnan Akmal couldn't hold on to a low diving catch off the thick outside edge.
De Villiers could have been out leg before wicket on 25 had Pakistan not wasted both their television referrals inside the first five overs of South Africa innings on Wednesday.
Umpire Rod Tucker turned down Ajmal's appeal but television replays showed the ball would have hit the middle and leg stump.
Pakistan also missed another chance to dismiss De Villiers on 37 when in Babar's first over with the new ball Khurram Manzoor could not judge a top edged sweep while running backwards from midwicket.
"Bowlers tried their best, but when you drop AB on zero and then again ... he is the kind of a player, he will make you pay for it," Pakistan bowling coach Mohammad Akram said.
Smith, 67 overnight, used his feet well against both spinners and seamers and raised his first century in 2013 with a straight driven boundary off Ajmal as South Africa progressed to 198-4 by lunch.
But once captain Misbah-ul-Haq took the second new ball and employed spinners, both Smith and De Villiers plundered Pakistan bowlers.
"Surely, it's hard work from here on," Akram said.
- AP