Mike Weir did not have long to savour his US Open first round lead with Lucas Glover replacing him at six under.

The 2003 Masters champion from Canada posted eight birdies undone by a double bogey at the par-four sixth hole to sign for a six-under-par 64, two shots clear of Sweden's Peter Hanson with former world number one David Duval three shots behind following a 67.

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But that lead had disappeared as darkness fell over Long Island with tournament officials trying to squeeze in as much play as possible having lost most of Thursday to heavy rain.

Weir dropped two shots over the first nine holes of his second round with American Lucas Glover replacing him at six under, four under for his round after 12 holes and heading to the clubhouse as overnight leader.

PGA Tour rookie Ricky Barnes was a shot behind Glover having played the back nine first while Weir was tied for third with Hanson, who had played 11.

Former Open champion Todd Hamilton was at three under after 10 holes in fifth place while Japan's Azuma Yano had shot up the leaderboard and was four under for his round after 12. That put him in a tie for sixth at two under for the tournament with Denmark's Soren Hansen, Adam Scott of Australia, American Sean O'Hair and England's Ross Fisher, who three birdies and a bogey playing the back nine first and had reached his 10th when the hooter sounded to suspend play for the night at 8:26pm local time.

American amateur Drew Weaver and Northern Ireland's Graeme McDowell were the best placed of the early starters from Thursday who were not scheduled to tee off until Saturday morning, their opening 69s good enough for a share of 12th place alongside Americans Gary Woodland, world number two Phil Mickelson and former world number one Duval.

Duval, who suffered an alarming dip in form following his victory at the 2001 Open Championship, was two over for his second round after 12 holes while Mickelson was level for his round having played 11.

Englishman Ian Poulter and Sweden's Johan Edfors were among a group of players at level par and waiting to begin their second rounds, joined by Americans Anthony Kim, JB Holmes and Canada's Stephen Ames, four under for the round after nine holes.

McDowell came off pleased with his protracted opening round but then saw the late starters in the 156-man field finally get their first rounds under way in drying conditions on still soft greens.

The Northern Irishman said he was certainly not getting carried away.

"I've led a few majors after day one," McDowell said. "It's not really what I'm trying to do. I'm just trying to stick around for the weekend. I'm trying to position myself as well as I possibly can and compete in Sunday afternoon."

The increasing number of under-par scores began to cause concern for defending champion Tiger Woods, who had been at level par with four holes to play but finished his round with a run of double bogey, bogey, par, bogey to leave him with a four-over 74.

"I was right there where I needed to be, and two bad shots and a mud ball later, here we go and I'm at four over par," Woods said.

England's Ian Poulter was happy to come home in even par as the morning wave completed their rounds while compatriots Fisher and Oliver Wilson and world number four Sergio Garcia of Spain later carded the same score.

"Good, solid start," Poulter said, "I'm very happy, three birdies, three bogeys, and it's a nice start to a US Open."

Garcia had dropped a shot as his second round reached the 12th hole with a birdie at his sixth, the par-four 15th, undone by a three-putt double bogey six on the 18th.

Poulter's compatriot Lee Westwood shot a 72, as did Northern Ireland's Rory McIlroy, who had improved to one over after 12 holes of his second round, while Wilson slipped to two over after nine.

Justin Rose will be thinking what might have been after carding a first-round 73 that saw him finish bogey, double bogey, bogey. He stayed in reverse gear at the turnaround, adding three more shots on his first nine to fall to six over.

Martin Laird, Scotland's lone competitor, and Darren Clarke of Northern Ireland shot four-over 74s and both fell further back. Laird was six over after 14 holes with Clarke slipping towards an early exit at nine over after 12.

World number three Paul Casey will need to get back on track on Saturday after posting a three-bogey, one double bogey first-round 75, the same score as fellow Englishman Simon Khan while Open and US PGA champion Padraig Harrington birdied the last for a first-round 76 .

English qualifiers Richard Bland, Simon Dyson and David Horsey, shot seven, eight and 11 over par scores respectively.