- Martin Kaymer scores second 65 in two days at U.S. Open
- German makes lowest 36-hole total in tournament's history
- Former world No. 1 holds six-shot lead over second-placed Todd Brendon
Martin Kaymer stretched his lead at the top of the U.S. Open leaderboard with a second successive round of 65 at Pinehurst No. 2 Friday.
The German's combined score of 130 over two days is the lowest 36-hole score in the history of the U.S. Open.
The record was previously held by Northern Ireland's Rory McIlroy who carded 131 (65 and 66) over the first two rounds as he went on to win the 2011 U.S. Open at the Congressional Country Club's Blue Course in Bethesda, Maryland.
"I played very well," former world No. 1 Kaymer told the U.S. Open website upon reaching the clubhouse. "I had some good rounds in the past as well. But yesterday and today, especially today, the way I worked my way around the course ... I hit some smart shots.
"I didn't play too aggressive and when I had a good number, I went for the flag and I didn't make many mistakes on the greens. I didn't three putt, I made a lot of good putts today and yesterday."
At 10 under par, Kaymer was six shots clear of second-placed American Todd Brendon going into the weekend, as he seeks his second major title.
Brandt Snedeker and Kevin Na were a shot behind compatriot Brendon at three-under-par while a group of five players including Dustin Johnson and Henrik Stenson were tied for fifth on two under.
Despite his considerable advantage Kaymer -- who won the U.S. PGA Championship in 2010 and picked up the Players Championship at Sawgrass last month -- refused to look beyond Saturday, where he hopes to maintain his lead.
"It's not a done deal," the world No. 28 said. "The last three, four holes, I got a little bit tired. I didn't swing as good as the first 14 holes."
Kaymer's wariness is perhaps understandable given a poor spell of form suffered over the last 18 months.
But current world No. 1 Adam Scott was less convinced by talk of Kaymer's perceived slow finish.
"If he does it for two more days, then we're all playing for second spot," the Australian told reporters.
Scott was tied for 14th position at level-par but still holds out a slim chance of catching the runaway leader.
"We all know that U.S. Opens get very difficult and if I can just somehow put together two really good rounds, maybe slowly but surely I'll creep my way up towards Martin."
Elsewhere on the course, two bogeys on the final three holes made for a disappointing finish for in-form young American Jordan Spieth, who ended the day at one-under-par, nine off the pace.
The 20-year-old, who tied for second at the Masters in April, was equal 10th alongside McIlroy (68), world No. 5 Matt Kuchar (70) and fellow American Chris Kirk (68).
Meanwhile, reigning U.S. Open champion Justin Rose shot a carded a 69 to finish the day at one-over-par after a difficult 72 on Thursday.
Six-time runner-up Phil Mickelson was tied for 33rd after a 70.
Masters champion Bubba Watson shot the same score, but missed the cut by one stroke following his opening 76.
Former world No. 1 Luke Donald will also miss the weekend rounds along with major champions Charl Schwartzel, Angel Cabrera, Geoff Ogilvy, Darren Clarke and Lucas Glover.