MIAMI (AFP) - World No. 1 golfer Lydia Ko was tied for the lead with Jang Ha Na at seven under when darkness halted play in the third round of the LPGA Coates Championship.

The New Zealander and second-round leader Jang, of South Korea, both completed six holes before the horn blew to end play at the Golden Ocala Golf and Equestrian Club course in Ocala, Florida, where the tournament was still playing catch-up after thunderstorms on Thursday.

Ko started the round one stroke behind Jang but made birdie on the par-three fourth to move into a tie for the lead.

While putting on the par-four sixth, Ko had to take a step back because she wasn't sure whether she brushed the ball at her address.

"Yeah, I wasn't sure because it's obviously getting a little dark, and with the steepness of the greens, you never know if it does move or not," she said.

"The rules, we cleared everything, so now I can just go to bed and have a good dinner and come out here early, but this happened to me last year at this tournament, the second round or something, and it happened at KPMG, too, so I just wanted to clarify it so it wouldn't be a problem tomorrow."

Jang, who also held the first-round lead, had a one-shot cushion over Ko and Japan's Haru Nomura after Friday morning's completion of the second round.

Jang's third round began with a birdie on the par-four opening hole, then she followed it up with a bogey on No. 2.

American Kim Kaufman got off to a fast start on Friday afternoon, moving into a share of the lead by making birdie on four of her first eight holes before dropping a shot at the par-four 10th.

Kaufman was tied for third at six under after 12 holes, along with Jessica Korda, Lexi Thompson and Nomura. Chinese Taipei's Candie Kung and Korean rookie Chun In Gee were tied for eighth at five under.

Chun, who will continue her round at the 10th hole on Saturday, bounced back from two early bogeys with three birdies in her last five holes of the day.

Players will not be re-grouped before the final round, which begins after the completion of the third round on Saturday.