Ko, Jutanugarn in US Amateur semis

New Zealand’s Lydia Ko and Ariya Jutanugarn of Thailand set up a semifinal showdown in the US Women’s Amateur with quarterfinal victories Friday at The Country Club.

The 16-year-old Jutanugarn, who successfully defended her title last week in the Junior PGA Championship, beat Erynne Lee 5 and 4. She also won the Canadian Women’s Amateur this summer and the 2011 US Girls’ Junior.

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

Canada’s Nicole Zhang will face Jaye Marie Green in the other semifinal.