By Mark Lamport-Stokes
PINEHURST North Carolina (Reuters) - Martin Kaymer, playing flawless golf, took advantage of a rain-softened Pinehurst layout to stretch his U.S. Open lead to a commanding eight shots in record style early in Friday's second round.
The 29-year-old German, three ahead overnight after opening with a five-under-par 65 that he described as "exceptional", followed up with the same score to post a tournament low 10-under total of 130 in the second major of the season.
Northern Ireland's Rory McIlroy had set the previous lowest score after 36 holes with an aggregate of 131 in the 2011 U.S. Open at Congressional.
"I played very well," a beaming Kaymer told reporters after hitting 12 of 14 fairways and reaching 15 of 18 greens in regulation on a challenging par-70 layout.
"I hit some smart shots, I didn't play too aggressive and when I had a good (yardage) number, I went for the flag.
"I didn't three-putt and I made a lot of good putts today and yesterday. You need a little bit of luck here and there, and that has been on my side so far."
Though more than half the field was yet to complete the second round on a sunny but relatively calm day at Pinehurst, Kaymer has already distanced himself in record fashion from his closest pursuers.
The largest U.S. Open lead after 36 holes is six shots, first achieved by Tiger Woods at Pebble Beach in 2000 before being matched by McIlroy in 2011.
Former PGA Championship winner Keegan Bradley, who carded a 69 on Friday while playing in the same group as Kaymer, was among six players who were tied for second at two under.
Level with Bradley were fellow Americans Brooks Koepka (68) and long-hitting Dustin Johnson (69), and burly Zimbabwean Brendon de Jonge.
Northern Ireland's Graeme McDowell, the 2010 U.S. Open champion at Pebble Beach, and American Kevin Na were at also at two under but yet to start the second round.
Kaymer, who gained a major confidence boost from his victory at the elite Players Championship last month, has played brilliant golf at challenging Pinehurst over the last two days.
His opening 65 included six birdies and a lone bogey and the former world number one was error-free on Friday despite having to contend with a few tough pin positions.
With barely a breath of wind on Pinehurst's fabled No. 2 Course which was softened by 0.64 inches of rain overnight, Kaymer birdied the 10th, 13th and 16th to reach the turn in three-under 32.
Seeking a second major title after clinching his first in the 2010 PGA Championship, he picked up further shots at the par-four third and par-five fifth to storm eight ahead of the chasing pack.
"I'm probably more surprised than anything," de Jonge said of being in a tie for second. "I didn't see 10-under out there. That's obviously very, very impressive.
"I'm under par through two rounds at the U.S. Open, so I'm very, very happy with that."
World number one Adam Scott, who had struggled with his short game on the way to an opening 73, clawed his way back up the leaderboard with a four-birdie 67 in the second round.
"I needed a good one today," said Scott. "I probably got the better end of the draw on the first two days, coming out early today after a bit of soaking rain overnight.
"On that front nine we could fire a little more aggressively at the pins. Hit some good shots and made some putts today. It still felt like hard work, but I'm very happy with the score."
England's Justin Rose, who launched his U.S. Open title defense with a 72, and Phil Mickelson, who has been a runner-up in his national championship a record six times and carded a first-round 70, were among the late starters on Friday.
(Reporting by Mark Lamport-Stokes, editing by Pritha Sarkar; Editing by Pritha Sarka)