* Horschel and Mickelson share lead halfway lead at one under
* Five other players one shot off the pace
* 68 players yet to finish second round
Phil Mickelson rolled in an 18-foot birdie putt in fading light at the 18th hole to grab a share of the lead in Friday's second round of the U.S. Open when play was suspended due to approaching darkness.
The putt gave Mickelson a round of two-over-par 72 for a total of one-under 139 and tied him with fellow-American Billy Horschel, who fired a dazzling 67 on a brutally difficult day at the weather-delayed championship.
The pair were perched atop a jam-packed leaderboard that had five players one shot back and another five golfers one more stroke adrift, with tournament favorites Tiger Woods and Rory McIlroy well within striking distance at three-over par 143.
Bunched at level par, were former world number one Luke Donald, his fellow Englishmen Justin Rose (through 17 holes) and Ian Poulter (14 holes), Steve Stricker and amateur Pan Cheng-tsung of Taiwan (nine holes).
Tied at one over par were Nicolas Colsaerts of Belgium, who shot 72, Australian John Senden (71), Jerry Kelly (through 12), Charley Hoffman (13), and 19-year-old amateur, Michael Kim of South Korea (11).
Sunshine on Friday replaced the rain that had plagued the tournament, the wind kicked up and players struggled to make par as venerable Merion Golf Club showed it was still a master test for the world's best golfers.
Sixty-eight golfers had not yet finished their rounds and were returning Saturday morning to the classic layout in the Philadelphia suburbs.
The projected cut to reduce the field to the top 60 and ties was estimated to come at seven over par after a round that saw players average nearly five over par.