Tiger Woods was among the players whose rounds were halted. They returned to the course after a 44-minute delay Thursday caused by another round of thunderstorms at the Merion Golf Club.
There was an earlier delay of 3 1/2 hours.
Phil Mickelson was the clubhouse leader, completing a round of 3-under 67.
Woods was 1 over when play was stopped the second time. He winced and shook his left arm after playing a shot out of the rough on the fifth hole, then bogeyed the hole to go to 2 over after play resumed.
Mickelson and Belgium's Nicolas Colsaerts (69) were the only players in the clubhouse under par.
Merion was as challenging as advertised, despite the onslaught of storms that softened the course during the past week. The slanting greens and heavy rough valued precision over power. Ian Poulter had quite the start, with only one par spaced among four birdies and three bogeys through nine holes on the way to a 71.
Mike Weir of Brights Grove, Ont., shot a 2-over 72. Mackenzie Hughes of Dundas, Ont., shot a 75. Calgary's Ryan Yip is another shot back. David Hearn of Brantford, Ont., finished his round with a 78. Adam Hadwin of Abbotsford, B.C., never even got to tee off.
Sergio Garcia birdied the 102-yard par-3 13th, but that was an aberration in a terrible start for the Spaniard, who has spent the lead-up to the tournament trying to make amends with Woods. Garcia had a quadruple bogey, double bogey and a bogey in his first five holes, but he later went birdie-eagle on the front nine on the way to a 73.
Garcia was greeted with mild applause and a few audible boos when he was introduced at the start of his round. He is playing his first tournament in the U.S. since a recent exchange with Woods hit a low point when Garcia said he would serve fried chicken if Woods came to dinner during the Open. Garcia has since apologized for the remark. He shook hands with Woods on the practice range this week and left a note in Woods' locker. He was also noticeably friendly to the gallery during Wednesday's practice round, stopping several times to sign autographs.
Garcia said he hasn't heard from Woods about the note, and he acknowledged there were hecklers in his gallery.
"I think there were a couple here and there," he said. "But there was — I felt the people were very nice for the whole day. I think that they, almost all of them, were behind me and that was nice to see."
Cliff Kresge, a Floridian ranked No. 551 in the world, hit the first tee shot of the tournament at 6:45 a.m. The horn blew at 8:36 a.m., and thunder, lightning and downpours followed, sending everyone scurrying for cover.
Safety was a concern on a course that required fans to take long shuttle rides from remote parking lots. At a fan zone, where a replay of the limited action was on a jumbo screen, a worker used a microphone to implore an overflow crowd to move to the merchandise tent.
"We're not feeling safe having this many people in here," he told them. Many folks heeded his message and moved on.
Any major weather disruption to the championship would be a shame, given that the U.S. Open waited 32 years to return to the course where Olin Dutra overcame a serious stomach illness to win in 1934, where Ben Hogan hit the picture-perfect 1-iron approach to No. 18 before winning in a playoff in 1950, where Lee Trevino pulled a rubber snake out of his bag at the first hole of the playoff when he beat Jack Nicklaus for the title in 1971, and where David Graham became the first Australian to win the trophy in 1981.
Thought to be too small to host an Open anymore, Merion had been off the radar for so long that many of the top names in the field — including Woods — had never played it until recently. Organizers had to be creative with the placement of hospitality tents and parking lots on the club's relatively small footprint, and ticket sales were capped at 25,000 a day instead of the usual 40,000 or so for recent championships.