Tiger Woods was cruelly denied another piece of history in the USPGA at typically sweltering Southern Hills today but nevertheless stamped his authority on the tournament after a remarkable second round of 63.

Woods required a birdie at the last for what would have been the first  62 in Major history but his putt, having initially appeared to drop, lipped out at the last possible second.

The world number one can console himself with the fact that he has moved two shots clear of the field on six-under with local favourite Scott Verplank his nearest challenger.

Paul McGinley heads the Irish challenge at the halfway stage, a round of 66 moving him to level par. Darren Clarke, who opened with a 77 on Thursday, matched the Dubliner's round to move to three-under, one behind Padraig Harrington who had a mixed day, shooting 73.

Graeme Storm had started the day as leader but finished a distant seven shots off the pace after a six-over 76 dropped him into a share of 15th at one over.

But the talk was all about Woods, who is on course to defend the title he won a year ago for the 12th and last of his major victories.

Of the six previous majors played at Southern Hills, each has been won by a 36-hole leader and if Woods plays anything like he did in the second round that statistic will be extended.

The world number one set the tone early with birdies at the first and fourth to get to one under for the championship before picking up another shot at the par-five fifth.

After a bogey at seven he closed his front nine with another birdie to go out in 32.

"It was an ideal start," Woods said. "I was three under through five and it just turned. I hit some nice shots out there."

A birdie at 10 got the back nine off to a good start but it was a par that really jump-started Woods.

After hitting into a bunker, Woods had a 35-foot putt for his four on the 12th and the putt found the left edge of the cup and dropped.

"That just kept the momentum of the round going, that was a big putt," Woods admitted. "Then from there I made a couple more birdies, which was nice."

Three straight birdies followed and with three holes to play that ground-breaking 62 was on the cards.

He failed with a 15ft birdie attempt at 16 but it was 18 where history looked like being made as his 18ft effort appeared set to drop into the cup before jumping out. An exasperated Woods dropped his putter to the green in disgust.

"I hit a good putt and I thought I made it," Woods said. "It would have been nice to have gotten a record and a three-shot lead going into the weekend. I hit a good put, that's the important part. It just didn't go in."

His closing tap-in capped a round that included eight birdies and a bogey. It was the 10th time in US PGA Championship history a player shot 63.

Verplank had held the clubhouse lead for a long time after a bogey-free 66 lifted him to four under.

"Obviously I played very well. I got in position where I could actually make a couple of putts," said the Oklahoma resident and local favourite.

Canadian Stephen Ames had the lead briefly at four under after consecutive birdies at the 13th and 14th but closed with a bogey on 18 to tie for third at three under after a 69.

"I'm hitting the ball nicely and getting it up and down when I need to, which is obviously the key to having a good score," Ames said.

Australian Geoff Ogilvy was as low as five under and tied for the lead with Woods late in his round but the 2006 US Open champion closed with a pair of bogeys to drop to three-under.

Harrington dropped to 19th after a three-over 73. He started his round with a birdie at 10 but followed it up with consecutive bogeys to drop to level par.

Harrington bogeyed 17 and 18 and closed his round with a bogey at nine with his only other birdie coming at the par three sixth.

"I had a disappointing bogey at the last. I would like to have been one or two better," Harrington said. "I'm not too bad, but I need to play better golf on the weekend."

The 1991 US PGA champion John Daly, who turned back the clock with a 67 in the first round, bogeyed his first two holes but held on well for 73 and a share of ninth place at level par.