New Zealand’s defending champion Lydia Ko is within striking range of the lead with a round to play at the LPGA Tour event in San Francisco.

Ko carded a steady one-under 71 in windy third-round conditions on Saturday to improve one place to fourth – three shots off the lead – at the Swinging Skirts Classic.

The outright leader on nine-under is still Canadian 17-year-old Brooke Henderson, whose 72 was spoiled by a bogey on her final hole.

Three birdies and two bogeys left the world No.1 Ko by herself on six-under, two strokes behind American Morgan Pressel and Korean Min Seo Kwak.

Ko, who celebrated her 18th birthday on Friday, opened with a 67 to lead after the first round but hasn’t maintained the same form.

Minjee Lee (74) is the best of the Australians at one-over par, while well off the pace are Sarah Jane Smith at eight-over, Karrie Webb at +10 and Katherine Kirk at +11.