Englishman Luke Donald sits atop the leaderboard at 4-under par.
ARDMORE, Pa. -- Family man Phil Mickelson, typically bold and unconventional in his tournament build-up, thrilled his fans by taking the clubhouse lead in the weather-delayed first round of the U.S. Open on Thursday.
Despite having arrived at Merion Golf Club in the early hours of the morning after an overnight flight from his native California, Mickelson soared into contention at the year's second major with a three-under-par 67.
Play was eventually abandoned for the day in fading light just before 8:30 p.m. (0030 GMT), following two earlier suspensions totaling four-and-a-quarter hours, with world number six Luke Donald leading at four under par after 13 holes.
"I feel like I'm in pretty good control of my game, and it's nice to get off to such a good start," Englishman Donald told reporters after making three consecutive birdies from the 11th, a curling nine-footer at the 13th giving him the outright lead.
Donald, a former world number one who has yet to clinch his first major title, was delighted to take advantage of a rain-softened Merion where there was very little wind but thick rough lying in wait as its main defence.
"You can attack the pins a little bit more, so it's playing as gentle as it might play so far," he said. "Today was a good day. I've got five holes left and five pretty tough ones to finish."
Masters champion Adam Scott was at three under after 11 holes while tournament favourite Tiger Woods, whose left wrist appeared to cause him pain on at least three occasions when playing out of the rough, was at two over after 10 holes.
Left-hander Mickelson, who carried five wedges but no driver in his bag to tackle Merion's short East Course, mixed four birdies with a lone bogey after setting off from the 11th hole in the second group of the day.
Mickelson equaled his lowest ever opening round at the U.S. Open, having previously fired a 67 at the start of the 1999 championship at Pinehurst where he finished in second place.
"Pretty good, a good start," Mickelson said after making do with just a few hours of sleep on his private jet while returning from San Diego where he had attended his oldest daughter Amanda's eighth grade graduation ceremony.
"I might have used just a little caffeine booster at the turn, just to keep me sharp, but that was our ninth hole or so and I just wanted to make sure I had enough energy. I feel great."
Long-hitting Belgian Nicolas Colsaerts opened with a 69 while former Masters champion Charl Schwartzel, fellow South African Tim Clark, Australian Jason Day and Americans Jerry Kelly and Rickie Fowler carded 70s.
Kelly had been just one stroke behind Mickelson before slipping back with a double-bogey at the tricky par-four 18th.
Long-hitting Americans Bubba Watson and Dustin Johnson, and English world number five Justin Rose, were among a group of 10 players knotted on 71.
Late starter Woods, seeking his first major title in five years, faced a short par putt on the 11th green before marking his ball after officials blew the horn to halt play for the day.
Woods had recorded two birdies, including a 50-footer at the sixth, but he also threw in four bogeys to leave himself with work to do when the first round resumes at 7:15 a.m. on Friday.
"I've got a lot of holes to play tomorrow, and hopefully I can play a little better than I did today," said Woods, who is hunting his 15th major title.
The siren had first sounded at 8:36 a.m. to halt the action under darkening skies, with Englishman Ian Poulter the early leader at three under par after recording birdies on his first three holes.
When play eventually resumed, however, Poulter immediately fell back with a bogey at the par-four 14th, where his drive ended up in heavy, wet rough and he ended his round with a 71.
Mickelson, runner-up at the U.S. Open a record five times, was at level par after five holes when play was suspended, and he mounted his charge after returning to the course.
The 42-year-old rolled in a breaking 25-foot birdie putt at the par-four first, then did well to save par at the fifth where his tee shot nearly ended up in a stream.
He knocked in a short birdie putt at the seventh before moving one stroke clear by sinking a 30-footer at the par-three ninth.
Mickelson was fulsome in his praise of Merion's East Course, which is staging its first U.S. Open in 32 years after long being regarded as too short to host a major.
"This is the best setup I've ever seen for a U.S. Open," he said. "It's a course that's withstood the test of time and it's challenging the best players in the world this week."
Though Merion is a short layout by modern standards, measuring 6,996 yards off the back tees, it is renowned for its thick rough, tilting fairways, contoured greens and several semi-blind shots.
While players were able to attack the pins on greens made more receptive by torrential rain during the championship build-up and again on Thursday morning, big numbers were waiting for anyone missing the fairway.
"It's a lot tougher than what they say it is," said 2011 Masters champion Schwartzel, who shared the early lead after making three successive birdies from the par-three 13.
"There are a lot of holes that are very penalising. I made three bogeys and that was all missed fairways."