They lead by one over Michelle Wie and by two over Anna Nordqvist.
Lydia Ko and Sarah Kemp head the Australasians in a share of 19th position and seven shots from the lead, a scores she shares with the world number one Stacy Lewis.
A win by Ko this week and a finish outside the top seven by Lewis would see the New Zealander became the world number one but there is a lot to happen for that scenario to be realised.
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