(Reuters) - South Korea's Park Sung-hyun charged to a two-shot lead after the second round of the U.S. Women's Open on Friday with the ominous figure of world number one Lydia Ko in hot pursuit. Park, who has three wins on the Korean Tour and is playing her first season on the LPGA circuit, birdied seven of her first 16 holes on the way to a sparkling six-under-par 66 at CordeValle Golf Club in San Martin, California. New Zealander Ko, seeking her third major title at the age of 19, followed her opening 73 with a seven-birdie 66 to surge up the leaderboard, finishing the day just three shots off the pace.
