Tiger Woods broke the Cog Hill course record with his best round this year to open up a commanding lead after the third day of the BMW Championship. Woods stumbled at the start, making bogey at the first hole, but was at his brilliant best after that, collecting eight birdies and an eagle in a round of 62.

That was enough to eclipse the previous course record of 63 he had shared with six others and give him a huge seven-stroke lead on 16 under over his nearest rivals heading into the final round.

"After I got past the first hole I was alright," Woods told reporters. "The round built upon itself. I bogeyed one right out of the gate then started at three to get it back."

Brandt Snedeker (66) and PGA Tour rookie Marc Leishman (68) were tied for second at nine-under while Padraig Harrington (69) and American Matt Kuchar were a further shot back.

"I've got to do something spectacular and he's got to maybe have a heart attack out there for me to have a chance," said Snedeker.

"That being said, if you go out there and play a solid front put some pressure on him, you don't know what is going to happen.

"That's my goal tomorrow, go out there and start fast."

Although Woods has not won a major this year, the American will still be chasing his sixth title of 2009 and his fifth overall at Cog Hill.

"I've always felt comfortable playing this golf course, even though it has changed this year," Woods said. "I did drive it good today, I've driven the ball well all week.

"This course has allowed me to get down there a little bit."

Woods' 62 was his lowest round at any event since he returned to the PGA Tour in March following reconstructive knee surgery.

He started the third day tied for the lead with Mark Wilson, who finished the day nine shots off the pace after shooting 71, but there were no indications of what was to come when he made a sloppy start with a bogey at the first.

He birdied the third then the sixth to get under par before roaring past his rivals with a birdie at then eighth then rolling in a 12-foot putt for eagle on the ninth and picking up five more birdies on the back nine.

"It just kind of built, a birdie-eagle to finish off the front nine," Woods said. "I kept making good shots, a couple of putts here and there and lo-and-behold I end up at nine-under par."