Kiwi Lydia has surged into contention at the Canadian Open in Saskatchewan, with a four under third round 68.
The 21-year-old was briefly in second at 10 under, but will start the final round four back of hometown girl Brooke Henderson, in a tie for seventh.
Ko, whose 15 LPGA wins include two majors, struck six birdies as the putter caught fire early on. There were also a pair of bogeys.
Meanwhile Henderson, 20, shot a 2-under 70 in clear and cool conditions to reach 14-under 202.
Jocelyne Bourassa is the only Canadian to win the national championship, accomplishing the feat in 1973 at Montreal Municipal in the inaugural La Canadienne.