THIRD ROUND LEADERBOARD:
(US unless stated)
-8 R Barnes -7 L Glover -3 R Fisher (Eng), D Duval -2 H Mahan, P Mickelson, M Weir (Can) -1 R Goosen (SA), B Watson, T Hamilton, O'Hair
Selected others: Level G McDowell (NI) +1 O Wilson (Eng), T Woods +2 S Garcia (Spa), L Westwood (Eng) +4 R McIlroy (NI) +7 I Poulter (Eng)
Barnes, ranked 519 in the world, was the 2002 US Amateur champion
Unheralded American Ricky Barnes maintained his halfway advantage to take a one-shot lead into the final round of the US Open at Bethpage.
Barnes completed a rain-hit third round 70 on Sunday to stay eight under par as Lucas Glover (70) remained seven under.
England's Ross Fisher (69) and David Duval (70) were third on three under.
Phil Mickelson struggled mid round but staged a strong finish to end two under after a 69, while Tiger Woods fought hard for a 68 for one over.
Hunter Mahan and 2003 Masters champion Mike Weir were alongside Mickelson in a tie for fifth, while two-time champion Retief Goosen, 2004 Open winner Todd Hamilton, Sean O'Hair and Bubba Watson were one under with one round left.
The 28-year-old Barnes, ranked 519th in the world and playing his first full year on the PGA Tour in his seventh year as a professional, led by one from Glover at the start of the day after Saturday's third round was suspended because of heavy rain with the pair on the 9th.
I would have liked to have shot a few more after I got to 11 over but I'll take two 70s
With 16 of the 60-strong field yet to start, play was delayed by a further four-and-a-half hours on Sunday because of overnight downpours, but on the resumption Barnes quickly stretched his lead to three over Glover after a birdie at the 2nd.
And when he holed a 30-foot eagle putt at the 4th, Barnes became only the fourth player to reach 11 under par at any stage in US Open history.
He equalled Jim Furyk's score from the 2003 US Open at Olympia Fields and was one shy of the record of 12 under, achieved by Tiger Woods at Pebble Beach in 2000 and Gil Morgan at Pebble Beach in 1992.
Barnes, who has missed six of 12 cuts this season and had a best of 47th last week at Memphis, bogeyed the 7th but his advantage grew to as big as six shots after eight as Glover dropped four shots in three holes.
The field behind was in a constant state of flux, but Mahan emerged from the pack to join Weir and Glover at four under after birdies on 13 and 14, though a double bogey at 15 dropped him back.
I made a couple of dumb shots but I hit a lot of great shots
Barnes, the 2002 US Amateur champion, faltered around the turn and dropped shots at 10 and 12. He birdied the 13th before leaking another bogey at 15, and despite a birdie on 17 he ended the day still just one ahead after another bogey on the 18th.
American Glover, whose whose only PGA win came at the 2005 Disney Classic, picked up three birdies coming home.
"I would have liked to have shot a few more after I got to 11 over but I shot even par in the third round at the US Open. I can't complain too much," said Barnes.
Mickelson, meanwhile, ignited the partisan New York crowd with a strong finish that included four birdies in his last six holes.
"It was very fun to do it," said Mickelson, who is in his last event before a break to be with wife Amy as she undergoes treatment for breast cancer in July.
"It was an up and down round. I made a couple of dumb shots but I hit a lot of great shots. There's a lot of birdies out there. Its awesome. It's such a great place."
The 39-year-old left-hander, a three-time major winner and four-time US Open runner-up, added: "If I can get a hot round going I can make up the difference. I'm one good round away."
Defending champion Woods began his day needing to match the record 11-stroke winning rally over the final 36 holes if he was to win a 15th major.
But after beginning with four straight pars, the world number one scrambled a bogey at the short 14th, his fifth, after taking two to hack out of thick rough, and found himself 14 strokes adrift.
Woods was struggling with his game, but made amends to roars from the gallery when he chipped in from the rough at the par-three 17th, his eighth.
I'm going to have to shoot a low round and probably get some help.
Further birdies at the 3rd and 4th took Woods to one over but he was unable to make up any more ground and will have to overhaul a nine-stroke deficit if he is to claim a record-tying fourth US Open and become the first player to successfully defend all four major titles
"I've hit the ball well all week, I just haven't got anything in the hole," said Woods, who has yet to win a major coming from behind after 54 holes. "I'm going to have to shoot a low round and probably get some help.
"It's not totally in my control. The only thing I can control is to shoot a low one. Hopefully I can get that done."
Fisher's iron play was impressive but he took 37 putts and missed half a dozen birdie chances to better his score as he attempts to become the first European winner at the US Open since Tony Jacklin in 1970.
"In a word, pretty shocking," said Fisher of his putting. "It's been the story of the week. It was a big relief when that putt on 18 dropped in. It felt like I was owed a few."
Graeme McDowell finished level par after a 69, Oliver Wilson ended one over after a round of 71 and Lee Westwood started strongly with two early birdies but slumped to a four-over 74 to end two over.
Sergio Garcia, meanwhile, finished two over after a 72, Rory McIlory finished four over and Ian Poulter carded 73 for seven over.
With only three hours' play possible on Thursday because of heavy rain, the tournament has struggled to remain on track and the final round will spill into Monday, the first Monday finish to regulation play since Larry Nelson won at Oakmont in 1983.
In the event of a tie, officials hope to stage the mandatory 18-hole play-off immediately after the final round on Monday, though more rain could force that into Tuesday.