By Mark Lamport-Stokes OAKMONT, Pennsylvania, June 20 (Reuters) - U.S. Open organisers on Monday said they regret "the distraction caused" by their delay in handing champion Dustin Johnson a one-stroke penalty until after Sunday's final round was completed. The U.S. Golf Association (USGA), however, stood by its decision to penalise Johnson one stroke after the round. USGA officials had raised the question at the 12th hole of whether leader Johnson would or would not be penalised for making his ball move on the fifth green, despite a ruling on site that he was not at fault. More...