|ANA Inspiration fourth round leaderboard|
|-15 P Lindberg (Swe), I Park (Kor), J Song (US); -14 A Jutanugarn (Tha), J Korda (US); -13 M Jutaugarn (Tha), C Hull (Eng)|
|Selected others: -7 L Ko (NZ), L Thompson (US); -6 B Law (Eng), Thompson (US); -1 C Matthew (Sco);+11 F Parker (Eng)Full leaderboard|
South Korea's Inbee Park and Swede Pernilla Lindberg will need an extra day to decide the winner of the ANA Inspiration in California - the first women's major of the season.
The duo played the par-five 18th four times but could not be separated before darkness fell at the Mission Hills Country Club.
Jennifer Song, who also finished on 15 under, had joined them in the play-off.
However, the American was eliminated after a par on the third extra hole.
Organisers had to use floodlights to illuminate the 18th green as Park, the Olympic champion and a seven-time major winner, made a six-foot putt fourth time around while Lindberg, who is seeking her first career title, followed with a two-foot putt.
The pair will start at the par-four 10th at 16:00 BST as the tournament is decided by a play-off for the second year in a row.
If they remain tied after the fifth extra hole they will move to the par-three 17th and then to the 18th again.
In 2017, it took 30 holes - 12 extra - to separate Chia Yen Wu and Lauren Stephenson in the US Women's Amateur.
England's Charley Hull finished joint sixth on 13 under after a double-bogey on the third hole while compatriot Jodi Ewart Shadoff was tied in ninth on 11 under.