Shane Lowry completed his third round in nerveless fashion to take a commanding four-shot advantage on the final day of the U.S. Open.
The Irishman, scenting a first major, held a three-stroke lead over Andrew Landry at the weather-affected tournament after completing a marathon 32 holes on Saturday at the testing Oakmont Country Club.
Lowry said he was confident of being able to hold it together on Sunday and did not appear to be feeling the pressure as he birdied two of the four holes still to be completed in his penultimate round to card a five-under 65 and go seven under.
The 29-year-old will take some catching when he tees off for his final round at 1530 local time in Pennsylvania after coming up with his best round of the week - and his lowest in a major - to make a clear statement of intent to his rivals.
Dustin Johnson joined surprise contender Landry in a share of a second place after managing a solitary birdie and making par at four of the five holes of a third round which he was unable to finish on Saturday.
American Johnson, who led after 36 holes, came agonisingly close to winning the U.S. Open last year and has work to do in order to end his wait for a major after going round 71.
World number 624 Landry recovered from back-to-back bogeys at 14 and 15 by making gains at the last two holes to card 70 as he continued to exceed expectations.
Lee Westwood and Daniel Summerhays are a shot further back on two under following third rounds of 69, while Branden Grace - not among the 25 players who returned for an early start on Sunday - is one under.
Sergio Garcia, also in search of an elusive first major, dropped back to level par after back-to-back bogeys at 15 and 16.