UPDATE 2-Golf-South Korean Ji birdies last to win U.S. Open

* Ji sinks 20-foot putt to birdie 18th for win

* Kung's final-round 69 leaves her one shot back

* Kerr slides back to tie for third with Kim

(adds details, quotes)

By Larry Fine

BETHLEHEM, Pennsylvania, July 12 (Reuters) - Ji Eun-hee of South Korea rolled in a 20-foot birdie putt on the last hole to win the U.S. Women's Open for her maiden championship title on Sunday.

The 23-year-old Ji's downhill putt completed an even-par 71 for a level-par 284 total which beat Candie Kung of Taiwan by one stroke.

"I was extremely nervous before that last putt," Ji told a television interviewer after thrusting her arms up in triumph on the last green.

Kung, who began the day five strokes behind overnight leader Cristie Kerr, fired a two-under-par 69 for 285.