Offaly's Shane Lowry is just two shots off the lead after carding a opening round 68 at the weather-delayed US Open at Oakmont.
Lowry hit birdies on 17 and 17 to continue his trend of shooting low scores in the first round.
"I've just not been able to put four rounds together and I don't know the reason for that," said Lowry, who shot 65 in the Phoenix Open and Players Championship, a 67 in the Honda Classic and 68 in the Masters.
"Weeks like this I tend to get my head around it. I know it's going to be tough gold and you are going to miss greens and make bogeys so maybe when I am like that I can accept bogeys a little easier."
Unheralded American Andrew Landry created history when he completed a four-under-par 66 for the lowest first-round score in nine US Opens when play resumed on Friday.
Landry was facing a birdie putt on the ninth, his final hole, when play was abandoned for the day on Thursday after thunderstorms dumped more than an inch of rain on the course.
He beats the previous record held by greats Ben Hogan in 1953 and Gary Player in 1973, both 67s.
Lee Westwood has put himself in contention for a long-overdue major title with his opening round of 67.
Westwood had four holes to play on Friday and completed them in two under par thanks to birdies on the eighth and ninth, the 43-year-old signing for a three-under-par 67, his lowest opening round in 17 US Open appearances.
The former world number one then received the welcome news that Thursday's early starters would not start their second rounds until Saturday after initially being given a start time of 8:43pm on Friday evening.
"I've been playing well and was really looking forward to coming back to Oakmont," said Westwood, whose tie for second with Jordan Spieth in the Masters extended his unwanted record of most top-three finishes in major championships without a victory to nine.
"I had a good experience here last time and I like a challenge. I picked up where I left off at the Masters and the last three events (which produced three top-15 finishes) and I'm very pleased to make a good start. You don't want to shoot a lot over par and have to chase.
"The Masters gave me a big boost. I had not contended in a big tournament for a while so it was nice to give myself a chance and feel those emotions again. I've had more chances (to win a major) at the Masters and the Open, but if look at my game, the US Open should suit me more than the others."
Meanwhile, Rory McIlroy will take an aggressive approach to try and rescue his campaign after slumping to an opening round 77.
The Co Down man bogeyed his last three holes to finish seven over par, equalling his worst ever score in the event.
"It was hard yesterday to get into any sort of rhythm and when you are not in control of your swing it was compounded by being so stop-start," said McIlroy, who carded eight bogeys and a solitary birdie.
"Right now I need to focus on hitting fairways and greens. I think I hit five fairways and eight greens which is not going to do anything. I hit irons off the tee on the first three holes and missed three fairways. With the course playing so soft I might just hit a lot more drivers and be as aggressive as I can.
"The toughest thing is trying to stay positive and not getting down on myself."
Half of the 156-strong field were unable to start their opening rounds on Thursday and only nine players finished, with American amateur Scottie Scheffler holding the overnight clubhouse lead on one under.
