World No 1 Adam Scott has admitted being too cautious after failing to take advantage as runaway US Open leader Martin Kaymer finally showed vulnerability on a brutally difficult Pinehurst No 2 course.
After posting the lowest total in US Open history through 36 holes to lead by six shots at 10-under, German star Kaymer's two-over-par 72 third round was still good enough to lead by five from Americans Rickie Fowler (67) and Erik Compton (67), a double heart transplant recipient.
Scott battled to a 73 and fellow Australian Jason Day a 72 to be three-over - a distant 10 shots behind Kaymer - in a tie for 16th and needing a miracle.
Kaymer could become only the seventh wire-to-wire US Open winner, joining Tiger Woods, Rory McIlroy, Walter Hagen, Ben Hogan, Tony Jacklin and James Barnes.
Not since Mike Brady squandered a five-shot lead in 1919 has a US Open 54-hole leader had such a margin and failed to win the title.
"I'm looking forward to see how I react to certain situations," Kaymer said. "Anything can happen. I can lead by seven or eight shots after nine holes. I can be down to all square. So it will be an exciting round.
"It'll be interesting how I handle it."
World No 2 Henrik Stenson (70), who could take Scott's No 1 status with a win if Scott finishes outside the top four, and Dustin Johnson (70) share fourth at two-under.
Aaron Baddeley, the only other Australian to make the halfway cut from 11 starters, shot 73 to be four-over and tied 23rd.
"I might have played a bit too cautious," Scott lamented.
"Today was a bit of a let down.
"Every round, I've got under par after the first half a dozen holes and only one day I've managed to keep it going so that's a little disappointing."
In extremely hot and dry conditions and playing a very tough course set-up that allowed only two sub-par rounds on Saturday, Scott started strongly with some impressive par-saving efforts over the opening four holes. He then pumped a drive down the par-five fifth and hit a beautiful six iron to two metres with his second. But his eagle putt lipped out forcing him to settle for a birdie. Rather than ride the momentum forward he bogeyed three of the four par threes, blunting his charge. - AAP