SOUTHAMPTON, New York (AP) — Ha-Neul Kim got the better of Korean compatriot Inbee Park to take the lead after Thursday's first round of the U.S. Women's Open.

Kim watched Park, the world's top-ranked player, moved to the top of the leaderboard in the morning session.

Kim, with an afternoon tee time playing the major for the first time, wondered, "Wow, how did she shoot that score?"

Then Kim went out Thursday and shot one stroke better, finishing with a bogey-free, 6-under 66 to take the first-round lead at Sebonack.

Park is trying to make history by winning the first three majors of the year. For a day at least, she was upstaged by a much less-heralded compatriot.

"I'm enjoying myself," Kim said through a translator. "I'm just happy to be here and to be playing in this big event. I'm not really thinking about winning or results but enjoying the moment."

Kim, a seven-time winner in South Korea, birdied her penultimate hole with daylight waning to claim the lead after Park held it for most of the day with her 67 in the morning session.

No player has won the first three majors in a season with at least four majors. The 2008 U.S. Women's Open champion, Park has already won five times this year, including her past two tournaments.

American Lizette Salas, Swedes Caroline Hedwall and Anna Nordqvist and South Korea's I.K. Kim shot 68.

Concerned about bad weather, tournament officials moved up the tees, and with the rain holding off, Park was able to play aggressively.

"I never had practiced from those tees, so I was a little bit shocked when I went to the tees," Park said.

"So instead of hitting like 5-irons, we were hitting 9-irons, and that was making the course much easier," she said. "I was actually able to go for some pins and give myself a lot of opportunities today. I made a lot of putts and didn't leave much out there."

Hedwall and I.K. Kim were each at 5 under with a hole left, but closed with bogeys. Nordqvist birdied her last two holes to pull into the tie for third.

The two Swedes grew up playing together.

"Certainly seeing her shooting 4 under in the morning session gave me a little bit of inspiration for the afternoon," Nordqvist said.

Chile's Paz Echeverria, a 28-year-old LPGA Tour rookie also making her U.S. Women's Open debut, and Canada's Maude-Aimee Leblanc shot 69.

Among eight players at 70 was Natalie Gulbis, who withdrew from a tournament and missed two others earlier this year because of malaria. Infected by a mosquito during the LPGA Thailand in late February, she returned for the Kraft Nabisco in early April. Gulbis hasn't finished better than 13th since, missing the cut at the LPGA Championship.

Defending champion Na Yeon Choi, second-ranked Stacy Lewis and 19-year-old amateur Kyung Kim were among 11 players at 71.

Lydia Ko, the 16-year-old New Zealand amateur who won the Canadian Open last August to become the youngest LPGA Tour winner, had a 72.

Michelle Wie opened her round with a quadruple-bogey 8 on No. 10. She was at 11 over through 14 holes before birdies on three of the last four to finish with an 80.

With Park's two major titles to start the year, South Koreans have won four straight majors. But Ha-Neul Kim was an unlikely representative to lead after the first round of this tournament.

"I was very nervous coming in, and I thought in the practice round that the course was very difficult," she said. "Before playing today I thought that even par would be a very good score for me."