Golf-Mickelson with one-shot lead at U.S. Open (Reuters)

* Mickelson aims for first U.S. Open title * Three-way tie for second at Merion (Updates at end of round) By Larry Fine ARDMORE, Pennsylvania, June 15 (Reuters) - Phil Mickelson birdied the long par-three 17th hole to seize the lead and will carry a slender one-shot advantage into Sunday's final round of the U.S. Open at the challenging Merion Golf Club. Mickelson rolled in a nine-foot putt at the 254-yard 17th to leapfrog playing partner Luke Donald, who slipped out of the lead with a bogey on the mammoth par-three. Four-times major winner Mickelson, looking for his first U.S. ...