Shane Lowry saw his lead cut to two shots as the final round of the US Open got under way at Oakmont Country Club.
The Irishman had completed a fantastic third round 65 in the morning to establish a four-shot advantage at seven under but a bogey on the second coupled with a Dustin Johnson gain on the same hole put the American within touching distance.
Spaniard Sergio Garcia and Scott Piercy were two under for their rounds and the week, with Jim Furyk making a charge to sit five off the lead.
South African Branden Grace and American duo Andrew Landry and Daniel Summerhays were also at one under, a shot clear of England's Lee Westwood.
Johnson looked like he meant business as he hammered a perfect 378-yard drive down the first but he could not take advantage while Westwood did well to get down in four after finding the bunker off the tee.
In the final group, Lowry made a nervy par putt to stay at seven under while Landry dropped a shot after failing to get on in two and fell five behind.
Piercy made a birdie-birdie start to join the group at two under alongside Grace who had a gain on the second, while Westwood dropped out of that group with a bogey on the same hole.
Another excellent drive from Johnson set up a birdie on the second as the 31 year old put his approach to three feet and the lead was cut to three.
That achievement with a devilishly difficult pin position was made to look even more impressive as Lowry and Landry both fell victim to the fast, sloping green to drop shots, with Grace also surrendering a stroke on the third.
Another Westwood bogey was to come on the third but Garcia started making a move in the other direction as a birdie on the fourth got him back into red numbers.
He was not making as big a move as Furyk, however, with the 2003 champion recording birdies on the first, fifth, seventh and 11th to also sit at one under.
Sumerhays had bogeyed the first to also slip into that group five off the lead but Garcia made a second consecutive birdie on the fifth to continue his upward trajectory.
