Lydia Ko, Ariya Jutanugarn advance

CLEVELAND -- Lydia Ko and Ariya Jutanugarn set up a semifinal showdown in the U.S. Women's Amateur with quarterfinal victories Friday at The Country Club.

Jutanugarn, from Thailand, beat UCLA's Erynne Lee of Silverdale, Wash., 5 and 4. The 16-year-old Jutanugarn successfully defended her title last week in the Junior PGA Championship. She also won the Canadian Women's Amateur this summer and the 2011 U.S. Girls' Junior.

"I tell myself I'm going to win it, not because I'm better than her, but to feel confident," Jutanugarn said. "Everybody here has a chance to win it. ... I played OK. My irons were better than yesterday. Today, when I missed an iron shot, at least it was on the green."

The 15-year-old Ko, the South Korean-born New Zealander who tops the world amateur rankings, beat South Africa's Paula Reto 3 and 1. Ko won the New South Wales Open in January in Australia at 14 to become the youngest player to win a professional tour event.

"Today was not my best," Ko said. "I didn't hit it as close to the hole, but I shot 2-under par, so it shows something was pretty good. We both could have played better but, in the end, in match play, it doesn't matter."

Canada's Nicole Zhang will face Jaye Marie Green of Boca Raton, Fla., in the other semifinal. Zhang, a 20-year-old player at Notre Dame, beat Australia's Su-Hyun Oh 2 and 1, and the 18-year-old Green topped Mexico's Marijosse Navarro, also 2 and 1.

Green got off to a nervous start, hitting the turf behind the ball on her opening tee shot, yet it bounced some 220 yards down the fairway and she halved the hole with a par.

"After I chunked my drive on the first hole, I got rid of the jitters," Green said. "I was so excited when that last putt went in. It was like I could breathe again."

The 36-hole final is Sunday.