Tiger Woods proved that he is still the top cat when he defied gusting winds to open up a four shot lead over five players including a combative Padraig Harrington at the halfway stage of the US PGA Championship at Hazeltine National.

Seeking his 15th major and a record-equalling fifth Wanamaker Trophy, the 33-year old erased the occasional smudge with the driver with some deft brushstrokes with the putter to paint another masterpiece - a two-under par 70-that left him at the top of the pile on seven under par as Harrington bogeyed the last for a 73 and three under.

Fatigued from last week's Firestone battle, Harrington was fading from the battle when he bogeyed three holes in a row from the 11th to slip three shots behind Woods.

But after matching the game's greatest player with a birdie at the driveable 14th, the never-say-die spirit kicked in and he produced the shot of the championship at the 15th when he hit a 301 yard three-wood from a fairway bunker that hurdled the front traps, hopped through the rough and nestled 12 feet from the pin.

"That's one of the best shots I've ever seen," Woods said. "He didn't mis-hit that. He hit it flush out of a bunker, uphill lie, where you can't use your legs to get any power and the chance of slipping is there but he still hit it flush enough to carry it that far.

"It was a pretty impressive shot and it was definitely worth the price of admission."

With the greens becoming bumpier by the minute, Harrington failed to convert the eagle chance, lipping out before matching Woods’ birdie to remain three behind.

It wasn't long before the gap was four as Woods rolled home a 18 footer for birdie at the signature 16th.

A sloppy Woods bogey at the last gave Harrington some hope but the Dubliner also failed to get up and down from the edge of the green, missing a ticklish three footer for par to slip back into a five way tie for second place with Vijay Singh, Ross Fisher, Brendan Jones and US Open champion Lucas Glover.

Disappointed with that finish, Harrington recovered his good humour in the press room when asked about the wonder wood to the 15th that so impressed Woods.

"He did say to me actually he would have paid to have seen it," Harrington said with a smile. "Did he tell you that? So I asked him for 50 bucks."

Harrington added:"Everybody's been talking about my shot out of the bunker, and I'm glad it came off because maybe I would be criticized for taking it on.

"I suppose at that time I had to push things on and I had to have a go at it ... Sometimes you've just got to go for those things and take a chance."

Harrington knows it will be tough to catch Woods in the final two rounds given the American's record.

The world number one has triumphed on all eight occasions when holding at least a share of the lead in a major after 36 holes.

"More and more tucked pin positions and with the greens getting a little bit firmer, all in all it's probably playing well into Tiger's hands," Harrington said. "But we'll have to put up with that. The firmer the course, somebody with a four-shot lead, especially Tiger, can pick and choose his shots now for the next two days."

As for Woods' record, he added: "I would go along the lines of it's got to break at some stage. Might as well tell myself that. In fairness to Tiger, that's never going to last forever. Maybe he'll be 60 when it's broken, but it's never going to last forever. Maybe I'll be the guy who does it. I suppose that's the way to look at it.

"At the end of the day I can't control what Tiger's going to do for the next 36 holes. But I have control over myself. So that's what I've got to focus on. Play my golf, be a bit more trusting. And if Tiger plays the golf he's capable of on the weekend, he'll be a winner. But if I play my golf, hopefully it will push him a little and we'll see what happens."

Harrington and Woods were the leading men in the main feature that saw Ross Fisher produce a tremendous cameo performance that saw him scorch into a share of the lead on six under only to bogey the last two holes for a 68 that left him tied with Harrington, Vijay Singh, Australia’s Brendan Fraser and US Open champion Lucas Glover on three under.

While all this was going on England’s Lee Westwood four under with two to play but double bogeyed the 17th, three putting from three feet to slip back to two under with Ian Poulter after a 72.

For a while to looked as though Rory McIlroy and Graeme McDowell would gatecrash the party but they faded over the closing holes to slip back to level and one over after respective round of 73 and 75

Ryder Cup skipper Colin Montgomerie said before the start that the European would have a major say this week and he was proved correct with Harrington, Fisher, Westwood,  Poulter and McIlroy all challenging.

All eyes were on the marquee showdown between Harrington and Woods and it didn’t disappoint as the went through the turn in one under par 35 to head into the back nine with the world number one a single stroke clear on six under par.

The back nine it was fascinating.

At the 10th, Woods came up short and three putted for bogey after Harrington rammed his 15 foot birdie chance four and a half feet past the hole. Gritting his teeth, the Irish star watched it lip into the hole on the low side to share the lead again on five under.

“Come on,” he appeared to urge himself as he walked off the green. It was pure golfing theatre.

Then came three sickening bogeys in a row as Harrington lost some focus and energy.

At the par five 11th, he put his approach in the trees and racked up his second bogey six of the day as Woods drained a 10 footer for par after troubles of his own.

The gap was soon two strokes after the 501-yard, par four 12th, where both men overshot the green but Woods holed from 10 feet for par and Harrington watched in agony as his six footer slid past on the low side.

Confessing he was shattered after last week’s showdown with Woods in Akron, the mistakes came thick and fast for Harrington who was bunkered at the par three 13th and thinned his recovery 30 feet past to slip two over for the day and three shots off the lead on two-under.

The Stackstown man needed treatment overnight for back spasms and iced his ankle and elbow before going out but declared himself fit for battle, insisting: "It's ongoing. I guess I'm paying a little bit for trying to get better. It's what it takes to get ready. It's just part of being a professional athlete."

He appeared to show no ill effects from his various injuries at the start of the day, chipping and putting for his par four at the first to tie for the lead after Woods dropped his first shot of the week when he pulled his drive and bunkered his approach.

After “halving” the second in pars, Harrington drove into a fairway bunker at par five second and racked up a six though Woods had to work hard for his par after ramming his birdie putt six feet past the hole.

At the sixth Woods regained the outright lead when he went to school on Harrington’s failed 30 foot birdie putt and rolled one home from around 25 feet to return to five under par.

The gap was two shots minutes later when Woods birdied the long seventh and and Harrington did well to avoid a bogey six after three poor shots in a row left him facing a six footer for par that he poured into the heart of the hole.

Nervous of the water left of the green, Harrington was buried in greenside rough on the right and almost chipped into the hazard on the far side of the green before getting up and down for his par after coming up short with his fourth.

One of the big turning points of the day came at the 432-yard ninth, where Woods hit a towering approach to six feet.

Harrington got inside him, however, firing his nine to just four feet. Woods missed and Harrington holed, cutting the gap to one with a putt that curled almost 360 degrees around the cup and fell in the side door to get him to five under par.

But this is not a two horse race.

Two-time US PGA champion Singh and reigning US Open champion Glover are lurking on three under par with Ernie Els, the winner of two US Opens and one Claret Jug, well placed to make a charge on one-under.

That he can win this week is a given for Singh, who has won 28 times since he turned 40. But given that 59-year old Tom Watson almost win the Open last month, Singh now believes he can keep on going for another decade at least.

“If he can do it at 59, I think I'll be able to do it in my 50s,” Singh said after his 72.

US Open winner Glover gave fair warning that his victory at Bethpage Black in June was no fluke when he added a two under par 70 to his opening 71 to join Singh on three under.

Like Singh, he can draw confidence from the knowledge that he has done it all before. He has nothing to prove and everything to gain

“I don't think I have to validate anything," said Glover, whose win at Bethpage Black was the second of his career.

Stiff winds and firming greens made conditions treacherous for the afternoon starters but that didn’t stop McDowell and McIlroy from making their presence felt.

Three behind Woods starting the day on two under par, McDowell birdied his third and fifth holes (the 12th and 14th) to grab share of the lead on four under before handing those strokes straight back at the the 16th, where he had to chip back into play following a pulled drive onto the bank of the creek, and the 18th, where he three-putted.

Back to two under par with nine to play, he limped home in 39 with bogeys the second, third, fourth and eighth and a solitary birdie at the seventh for 75 that left him on one over.

McIlroy looked to have damaged his chances by opening with a pair of bogeys but the 20 year old Holywood kid roared back into the mix when he rolled home a curling 40 footer at the eighth to complete a hat-trick of birdies.

Despite a bogey six at the 11th, he bounced back again with birdies at the 14th and 15th but drove into the creek at the 16th, double bogeyed the par three 17th with a three putt and lipped out with a birdie chip at the last for a 73 for a level par total at halfway.