Dustin Johnson will take a one-shot lead into the third round of the US Open after the tougher conditions at Oakmont Country Club helped keep challengers at bay as round two was completed.
Half the field had to play their second rounds on Saturday after Thursday's weather delays, with American Johnson completing rounds of 67-69 on day two to sit at four under alongside countryman and first-round leader Andrew Landry.
As Landry fell back in the early stages of his second round, Johnson was twice overtaken by Lee Westwood and Grégory Bourdy but both players would slip back to leave the 31 year old on top of the leaderboard.
World Number 624 Landry's challenge looked to be fading as he turned in 39 but birdies on the 13th, 17th and 18th moved him back within one shot of the leader and a shot clear of Frenchman Bourdy, Spaniard Sergio Garcia, Ireland's Shane Lowry and American Scott Piercy.
Westwood eventually signed for a 72 to sit at one under alongside fellow Englishman Andy Sullivan and American duo Jim Furyk and Daniel Summerhays, with just ten players under par.
Westwood had been the first man to make a move as he put a brilliant approach to three feet on the first and then found the par five fourth in two to move to five under.
But the 43 year old would record six bogeys in nine holes from the sixth before birdies on the 16th and 18th kept him well in the hunt for a first Major Championship.
Bourdy was the next man to move to the summit as he recovered from an opening bogey with lengthy putts on the fifth and ninth and a brilliant approach to the sixth to turn in 33.
The 34 year old then holed his second shot on the 11th from 137 yards for an eagle and birdies on the 13th and 14th had him out in front on his own.
A bogey on the 16th was then followed by a double on the last but the unruly finish failed to take the gloss off an excellent 67.
"It was a beautiful round of golf and I knew at the beginning of this week, I could do something well," he said.
"I feel very good in my game the last few weeks, and I really love the difficulty of this course. I can play some great tee shots, good irons.
Today I holed some putts as well, so A-plus. At the end it was a very good day on a very difficult course like this - Grégory Bourdy
Lowry had initially fallen back with bogeys on the tenth and 16th but he made gains on the fourth and sixth before making a brilliant par save on the ninth.
South African Louis Oosthuizen returned in the morning to complete his second round and signed for a brilliant 65 to sit at level par alongside England's Lee Slattery, a shot ahead of Scot Russell Knox.
World Number Three and 2011 champion Rory McIlroy could not recover from an opening 77 as he finished his 71 with a double-bogey to miss the cut.
The third round is expected to be completed on Sunday morning before a champion is crowned in Pennsylvania.