Jason Dufner carded a course record of 63 to move to the top of the leaderboard following his second round of the US PGA Championship at Oak Hill.

The 2011 runner-up had a birdie chance on 18 to become the first man ever to shoot 62 in a Major, but he left his putt short, before nervously converting the par effort to finish on nine-under-par.

His round got off to a strong start when he holed his second-shot approach for an eagle at the second, and he picked up more shots with birdies at four and five.

The morning's rain had slowed down the greens and Dufner took advantage of the kind conditions to sink further birdies on 11 and 13.

An excellent approach shot on 16 resulted in the American's fifth birdie of the day, and another into 18 gave him the opportunity to make Major championship history, but it wasn't to be.

He currently leads by one shot from compatriot Jim Furyk, while Adam Scott and Matt Kuchar are a stroke further back at seven-under-par.