Inbee Park birdied the final hole for a 5-under 67 and a one-stroke lead over Michelle Wie, Ariya Jutanugarn and Hur Mi-Jung in the HSBC Women's Champions.
The 27-year-old Wie, who has struggled with injuries and form since winning the US Open in 2014, shot a 6-under 66 at the new Tanjong course. "I did make a couple good birdies down the stretch, and this golf course, you've got to stay in it as long as you can", she said, crediting her short game for helping keep her in it during Saturday's delayed third round.
"It just shows how well the girls are playing and you know how many birdies are actually happening", said Ko of her fellow competitors.
Bjork had a 67 to match Jamieson at 10-under 132 at Pretoria Country Club.
Ko's main rival for the No 1 spot, Ariya Jutanugarn, is tied for second along with Sung Hyun Park. "I think it's going to be a putting game tomorrow and somebody that putts really consistently well, I think is going to have the best opportunity to hold the trophy at the end of tomorrow".
Ko's putter was running hot with six birdies in 10 holes - including birdies on the first four holes - to help her to a five-under par score in the third round of the tournament. Wie was four-under par through nine holes.
Defending champion Ha Na Jang is three shots off the lead and T-5 at 11 under for the tournament.
Almost three hours of play was lost to early-afternoon rain but it didn't halt the momentum of Ko, who is playing her third tournament of the season after a relatively muted start by her standards.
"I went to the Honda and kind of stole him away for a little bit". "That's what I've been trying to do the past few days, and that's the mind-set I've got to take on to tomorrow, because there are birdies out there".
Wie has had a number of injury issues over the years but she played pain free today and was delighted to do so. When I hit bogeys, I thought it was like I just missed some shots. Although I realized I was not committed to my shots like I was before the rain, I tried to pull myself back.
Pettersen also briefly found herself in front after making seven birdies, including three in a row from the 10th, only to drop two shots in her last four holes.
Wie, the victor of four LPGA Tour events including the 2014 US Open at Pinehurst, struggled for much of a year ago recording only one top ten in 25 starts in 2016.