By Mark Lamport-Stokes OAKMONT, Pennsylvania, June 17 (Reuters) - American Dustin Johnson ended a marathon Friday at the weather-disrupted U.S. Open with the clubhouse lead, carding a one-under-par 69 shortly before second-round play was suspended for the day. The long-hitting Johnson, who was a runner-up in last year's U.S. Open one stroke behind Jordan Spieth after three-putting the final hole, produced superb form from tee to green as he posted a four-under total of 136 at Oakmont Country Club. Also at four-under was surprise first round leader Andrew Landry, a PGA Tour rookie who will only start the second round on Saturday morning after the year's second major championship was knocked off schedule by multiple thunderstorms on Thursday. More...