Oakmont - Unheralded Andrew Landry rolled in a 10-foot birdie putt to cap a first-round 66 on Friday, taking a three-stroke clubhouse lead as the rain delayed US Open went into overdrive.
The 28-year-old Texan, ranked 624th in the world, had six birdies in his four-under effort, the lowest first round score in the nine US Open championships held at Oakmont.
He had been left with that one putt at the par-four ninth to finish off the round when play was halted for the third time on Thursday because of thunderstorms, but said there was little angst involved despite a wait of some 15 hours.
"It was a pretty easy putt to make," said Landry, who found himself three strokes clear of the field after New Zealand's Danny Lee bogeyed 16 to fall into a group at one-under.
Two-time Masters champion Bubba Watson, who was tied with Lee at two-under when play was halted on Thursday, also returned with a bogey at 16.
England's Lee Westwood, Ireland's Shane Lowry and Americans Harris English and Kevin Streelman were also on the course at one-under -- while amateur Scottie Scheffler made it into the clubhouse on Thursday with a one-under 69.
Scheffler was one of just nine players to complete the first round on Thursday, and scheduled afternoon starters including world number one Jason Day, five-time major winner Phil Mickelson and world number six Dustin Johnson never made it to the first tee.
The delays have the tournament shaping up as an endurance test on an Oakmont course still showing plenty of teeth, despite being softened by rain.
Round one resumed at 13:30, and the first wave of round two was to begin around 19:45 with organisers targetting a mid-day finish on Saturday - to be followed promptly by the start of round three.
"You've just got to do one shot at a time," Streelman said of the upheaval. "You say it all the time, but it's really true, especially in this circumstance."
Flexibility will be key, Streelman said, as players cope with the changing face of Oakmont, where the rain made greens and fairways slightly more receptive, but only made the rough more difficult.
"It's a different golf course now," Streelman said. "I don't think it's necessarily easier or harder. It's going to take someone who is a chameleon to be able to adjust and there's going to be some birdies to be made, but the trouble's still out there."