Ryder Cup teammates Patrick Reed and Jordan Spieth charged up the leaderboard, but the American assault on Friday didn't include Tiger Woods who crashed out of the US Open.
The two Texas natives were co-leaders after 36 holes at the $10 million tournament at the 7,695 foot Chambers Bay golf course, the longest in major championship history.
The 24-year-old Reed had a 69 for a five-under total of 135, joining reigning Masters champion Spieth, 21, who had a fine 67.
"Anytime I play with Jordan I enjoy it," said Reed. "The main thing for me is to stay focussed
"I am in a good position and I hopefully can have a good weekend and a chance to win."
Overnight co-leader Dustin Johnson was one stroke adrift with a 71 as he was tied with South Africa's Branden Grace (67) who was the only non-American in the top four. US golfers held eight of the top 11 positions on Friday.
Grouped on 137 were US trio Tony Finau (68), Daniel Summerhays (67) and Ben Martin (70) and Joost Luiten of the Netherlands (69).
The two young Americans Spieth and Reed formed a successful Ryder Cup pairing against the Europeans at Gleneagles, Scotland in late September.
World number two Spieth is once again proving he can shine on the biggest stage as he surged up the leaderboard by making birdies on three of four holes beginning at No. 14.
Spieth, who posted a wire-to-wire victory at Augusta in April, is seeking to become the first man to win the Masters and US Open in the same year since Woods in 2002.
"If you shoot in the 60s at a US Open you are going to be pleased," Spieth said. "I will draw on my experience at Augusta, but my patience here has to be that much higher.
"At Augusta I was making everything. It would be nice if I could do that here. This course is going to get tougher and tougher."
There was some drama on the final hole of the day for Spieth's threesome when playing partner Jason Day, of Australia, collapsed on the side of the fairway after suffering a bout of vertigo.
The Queensland native was treated by several medical staff on the course for about 10 minutes before mustering enough courage to finish out his round despite being in obvious discomfort as he made those final shots.
His manager Bud Martin said Day, who shot a 70, expects to be well enough to resume his tournament on Saturday.
Reed also climbed up the leaderboard Friday as he briefly held the tournament lead, but a bogey at the last dropped him into a tie with Spieth.
Reed, who proclaimed himself as one of the "top five players in the world" after winning the WGC-Cadillac Championship in March of last year, would like to validate that boast with his first major title at Chambers Bay.
Reed had a chance to hold onto the 36-hole lead but his 18-foot putt for par on 18 stopped on the edge of the cup for a tap in bogey.
Johnson had three birdies on the front nine and appeared to be headed into the weekend with at least a share of the lead.
But the long-hitting American had a frustrating finish with back-to-back bogeys on 17 and 18 to drop to a tie for third.
"When I got into trouble I felt I hit good shots and got myself out and made some good up-and-downs," said Johnson, who is considered one of the best players who hasn't won a major. "But I just didn't hole the putts like I did yesterday.
- Longest major in history -
The USGA wanted a more difficult second round after 25 players broke par on Thursday. So they extended Chambers Bay to 7,695 feet, making it not only the longest ever US Open but also the longest in major championship history.
The front nine alone was 4,020 feet. They also made the first hole a par-five instead of a par-four and altered 18 so that it became a tricky par four.
World number one Rory McIlroy and six-time US Open runner-up Phil Mickelson both punched their tickets into the weekend.
McIlroy was making no progress from the two over mark he started the day on until he eagled the par-four 12th.
But he took a double-bogey at the par-three 17th and settled for a second straight 72 and a four-over total which got him into the weekend.
Woods wasn't so lucky as he had the door slammed shut behind him Friday.
The fallen great made for the exit door after a struggling second round score of 76 failed miserably to repair the damage done by a horrendous opening 80.
That effort -- his worst at any US Open and the fourth worst of his pro career -- left the sport's former dominant force with a mountain to climb just to make the cut.
Source: AFP
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