Lydia Ko and Jaye Marie Green advanced to the 36-hole final in the U.S. Women's Amateur, winning semifinal matches in wet and windy conditions Saturday at The Country Club.

The 15-year-old Ko, the South Korean-born New Zealander who tops the world amateur rankings, beat Thailand's Ariya Jutanugarn 3 and 1.

"Getting to the final feels really good," Ko said. "My putts were rolling today, which really helps the confidence. This is amazing to beat such a great player."

The 18-year-old Green, from Boca Raton, Fla., edged Canada's Nicole Zhang 2-up.

"Just knowing I'm still in the running to be the United States champion gives me the chills," Green said.

At 15 years, 3 months, 18 days, Ko is the second-youngest finalist in Women's Amateur history, and could become the second-youngest champion. Both records are held by Kimberly Kim, who was 14 years, 11 months, 21 days when she won the 2006 tournament. Ko won the New South Wales Open in January in Australia at 14 to become the youngest player to win a professional tour event.

Ko chipped in from 45 feet on the 15th for a birdie to halve the hole. At the 450-yard, par-5 16th, Ko hit the green in two shots and two-putted for another birdie to again go 2 up.

The deciding birdie came at the 17th. Jutanugarn missed the green while Ko hit her approach to 8 feet. Jutanugarn made one stab at it, hitting a chip from deep, matted rough that went 60 feet right of the hole. She conceded Ko's birdie putt to end the match.

"She's really a great player and an amazing putter," Jutanugarn said.

Green birdied the par-3 11th to take a 3-up lead, but Zhang fought back.

"I hung in there the whole way," Zhang said. "I didn't give up at all."

Zhang won the par-5 12th with a birdie and Green's lead was trimmed to 2-up. At the 14th, a par 3, it looked as if Zhang would win another hole. Her ball was 20 feet from the hole, while Green sprayed her tee shot far to the right, some 90 feet from the hole and in the rough.

Green followed with a fine pitch shot over a bunker to 6 feet. When Zhang missed her birdie putt, Green banged her putt into the back of the hole to retain her lead.

"To get up and down there, that definitely helped my confidence and kept me 2 up," Green said.

Zhang won the par-5 16th with a birdie. She challenged the fairway bunker on the right, cutting the dogleg and flying her tee shot some 60 yards past Green, who was in the bunker. Zhang hit the green in two shots, easily making a birdie to win the hole.

Green was 1-up with two holes to play. They halved the 17th. At the par-4 18th, Zhang had to win the hole to extend the match. Green's approach shot came first and she hit a beauty that flew over the flagstick and nestled 18 feet from the hole. Zhang's approach shot from 138 yards was right at the flag, but a gust of wind knocked the ball down, 10 feet short of the green. When Zhang could not hole her chip, she conceded Green's birdie putt and the match.

"She hung in there the whole time," Green said. "I feel like I'm dreaming."