Tiger Woods, meanwhile, remained well off the leaderboard at soggy Bethpage Black.
Barnes, the 2002 U.S. Amateur champion, set the U.S. Open 36-hole scoring record by finishing two trips around the course in 8-under 132. He completed his second round Saturday morning, making three birdies in nine holes for a 65 and ending up one shot ahead of Lucas Glover (64) and two up on first-round leader Mike Weir (70).
The previous 36-hole record was 133, set by Jim Furyk and Vijay Singh at Olympia Fields in 2003 and matched Saturday by Glover, who completed his round shortly before Barnes posted his score.
The cut was 144, 4 over par, with 60 players ' the minimum possible ' qualifying for the final two rounds.
Woods, the defending champion, was tied for 41st, 11 shots behind Barnes. The third round was to begin later Saturday afternoon, with the USGA hoping rain bands that had passed over Bethpage earlier in the day were gone, at least for a few hours.
You never know, Woods said. Ive got 36 more holes, over the next probably three days. Its one of those things where if I keep plugging along, just like any U.S. Open, keep plugging along, make a birdie here and there and well see where it ends up.
Barnes has hit 31 of 36 greens this week; the rest of the field is only hitting the green in regulation about half the time.
If you would have told me I would have been 8 under and only (a) one-shot lead, I would have said, Youre kidding me, Barnes said. But Ill take it. It was solid play. And Im happy with the position Im at.
Woods was not.
The defending champion and worlds No. 1 shot 69 on Saturday, getting to 3 over for the week and making the cut with only one stroke to spare. He missed a 10-footer for par on his closing hole, then swiped his putter in frustration before tapping in to end his four-birdie, three-bogey day.
Glover had a chance at matching the U.S. Open and all-time major championship record with a 20-foot birdie putt on his final hole Saturday morning, only to leave it short and settle for a bogey-free 64.
Glover said he was thinking about shooting 63 as he stood over the putt, then lamented that he weenied out.
He didnt have much else to complain about.
Im very pleased, said Glover, who didnt even make the cut in any of his three previous U.S. Opens. Probably as good a round of golf as Ive played. Im very excited.
Three players, including David Duval, were tied for fourth at 3 under through 36 holes.
Im just happy Ive given them a good show so far, Duval said.
Azuma Yano of Japan shot 65 in his second round, joining Duval and Swedens Peter Hanson at 3 under. Steve Stricker made a big move as well, shooting 66 to move into a tie for 11th at 1 under.
Light rain started falling around midday Saturday, then stopped about four hours later. Much work has been done at Bethpage to get rid of the water that turned the park into a pool on Thursday, but any significant new rainfall would likely make the Black unplayable once again.
Its been a lot of starting and stopping this week, Weir said. Its just been a test of patience and trying to be in the right state of mind each time you come out not to let things change too much. Its difficult for everybody.
The forecast for Saturday night and Sunday was downright miserable, and some players didnt think there was a chance of this tournament having the traditional Fathers Day finish.
Aint gonna this year, Duval said.
Phil Mickelson took a drop on the way to making bogey at the par-5 13th for the second straight day, and wound up shooting even par 70 to go to 1 under for the tournament.
Im only what, six back? Were only halfway through and were all going to be playing under the same conditions now, said Mickelson, who wound up seven behind Barnes. I like the position Im in.