American Ricky Barnes took a one-shot lead into the final round of the US Open at Bethpage Black but it could have been so much better.

Barnes shot a third-round 70 to stay at eight-under-par through 54 holes, one clear of compatriot Lucas Glover and five ahead of England's Ross Fisher and American David Duval as the 60-man field prepared to make a quick turnaround and head back out to get the final round under way.

Australian rookie Michael Sim is poised for his first top-20 finish at a major, continuing his consistent tournament with a third-round 71 to sit in a tie for 20th at two-over, 10 strokes behind Barnes. Adam Scott is at three-over following a third-round 73, while 2006 champion Geoff Ogilvy had a disastrous round of seven-over-par and is now in a share of 42nd.

As the second major of the year headed for a first 72-hole Monday finish since 1983, Barnes had threatened to set more records after shooting the lowest 36-hole total in US Open history, 132, after a 65 in the second round.

Barnes, playing his first full year on the PGA Tour in his seventh year as a professional, held a six-shot lead at 10-under at the turn and was going the right way about emulating 2003 British Open champion Ben Curtis in making his maiden professional victory a major success.

A long-range eagle putt at the fourth hole had sent the 28-year-old to 11-under par, the first man to move into double digits at the US Open since Jim Furyk in the third round at Olympia Fields en route to his victory in 2003.

Bogeys at the seventh and then the long and difficult par-fours at 10 and 12 as Glover birdied the 10th and 11th saw Barnes' lead slip to two shots at eight-under.

Although he sank a 25-foot birdie putt at 17, he gave the shot back at the last, producing a great shot out of thick greenside rough only to miss from five feet.

Fisher finished strongly, the Englishman sinking a 10-foot birdie putt at 18 for a 69 to move to three-under ahead of the final round, which will see him play with Duval, who also closed with a birdie for a 70 to join him in a tie for third.

Canada's Mike Weir fell back to two-under with a 74, where he was met coming the other way by American duo Hunter Mahan, with a 68, and world No.2 Phil Mickelson, who delighted his big following of fans by sinking a 38-foot birdie putt at the 18th for a 69.

Two-time US Open winner Retief Goosen shot a second 68 in a row and Bubba Watson carded a 67 for both to get to one-under, with Sweden's Peter Hanson and Americans Sean O'Hair and Todd Hamilton.

Defending champion Tiger Woods began his day 11 shots behind Barnes's overnight lead and bogeyed the 14th, his fifth of the day, to fall 14 shots off the pace.

Woods made amends to the delight of his huge gallery when he chipped in from the rough at the par-three 17th, his eighth, and the world No.1 sent down back to back birdies at his 12th and 13th holes to reach one-over.

Oliver Wilson shot a 71 to end the third round at one-over for the tournament and Sergio Garcia of Spain went over par for the first time all week when he shot a 72.

More heavy rain had fallen at Bethpage Black overnight, saturating an already drenched course which had flooded on many greens and fairways on Saturday evening, bringing play to a premature end with the third round only just having got under way.

That led tournament officials from the United States Golf Association to suspend play for the day and with the storms continuing through the night, and a further three-quarters of an inch of rain landing on the Black course, officials decided to delay play until noon, pushing fourth-round play back into Monday for the first time in 26 years.

Having managed to get the final round started before nightfall, USGA officials were confident of finally getting the tournament finished on Monday, providing they avoided further stoppages.