Richard Bland upstaged a star-studded field to earn a share of the U.S. Open lead at the halfway stage as defending champion Bryson DeChambeau soared up the leaderboard.

Unheralded Englishman Bland, 48, powered to the top of the summit at Torrey Pines thanks to his four-under-par 67 in San Diego, where he continues to prove patience pays off.

Alongside Russell Henley (70) for the one-stroke lead after two rounds, Bland is benefitting from perseverance, having gone almost 20 years without a European Tour title.

At the 478th attempt on the European Tour last month, Bland claimed an emotional win at the British Masters, which earned him a place in his fourth major championship.

Bland – who missed the cut at his one previous U.S. Open appearance in 2009 – dazzled on day two of this year's tournament, storming into the clubhouse lead before being joined by American Henley.

After opening with a 70, Bland holed seven birdies and three bogeys to catapult himself to the top of the standings, before Henley teed off in his second round, amid his improbable dream of clinching a major.

"I feel good about my game," said three-time PGA Tour champion Henley, whose previous best performance at a major came via an 11th-place finish at the 2017 Masters.

"I've never been in this position before in a major. Just feel like I'm going to learn something no matter what happens."

Louis Oosthuizen (71), who was the overnight co-leader along with Henley, ended day two in a tie for third position alongside Matthew Wolff (68), while Bubba Watson (67) and Jon Rahm (70) are a shot further back at three under through 36 holes.

DeChambeau boosted his hopes of back-to-back U.S. Open titles, though the big-hitting American star remains five strokes off the pace heading into the weekend.

A two-under-par 69 saw DeChambeau move to even par as he rose 47 positions into a tie for 13th alongside rival and two-time U.S. Open champion Brooks Koepka (73), Justin Thomas (69), Collin Morikawa (67), Harris English (70), Branden Grace (70), Christiaan Bezuidenhout (70) and Adam Hadwin (72).

Koepka – eyeing a fifth major crown – lost ground on the leaders after mixing five bogeys and just three birdies, while Rory McIlroy followed his opening-round 70 with a 73 to be one over the card as world number one Dustin Johnson (73) ended the day two over.

US PGA Championship winner Phil Mickelson emerged from the jaws of elimination, qualifying for the weekend via a two-under-par 69 after his forgettable 75 on Thursday.

Masters champion Hideki Matsuyama (76), Adam Scott (75), Sergio Garcia (74), Patrick Reed (73) and Jordan Spieth (69) all avoided the cut, but Justin Rose (77) was not so fortunate at 13 over.

Louis Oosthuizen joined Russell Henley in a share of the lead as the opening round of the U.S. Open was interrupted, while Phil Mickelson's quest for back-to-back majors got off to an awful start at Torrey Pines.

A fog-enforced delay meant the start of the major tournament was pushed back by around an hour and a half on Thursday, and while Oosthuizen was unable to finish his round, the 2010 Open Championship winner still ended the day alongside Henley atop the leaderboard.

Oosthuizen – one of three players to finish in the top 10 at each of the last two U.S Opens, joining Rory McIlroy and Xander Schauffele – moved into a tie at four under after birdieing the 14th hole in San Diego.

Henley had set the early pace after claiming an early lead behind his impressive four-under-par 67, which was enough for him to initially head back to the clubhouse with a one-shot lead over Francesco Molinari and Rafa Cabrera Bello.

It was Henley's sixth career score of 67 or better in a major championship and first since the 2018 US PGA Championship (65 in round two).

Molinari and Cabrera Bello remain a stroke off the pace heading into Friday, with the first round scheduled to resume at 06:50 local time.

Two-time U.S. Open champion Brooks Koepka is not far behind following his two-under-par 69 to kick off his pursuit of a fifth major crown.

Koepka, who finished second behind Mickelson at the PGA Championship, set the standard with four birdies in his first 11 holes taking him into a solo lead.

However, two bogeys meant he had to scramble to recover as Koepka ended the day alongside Schauffele, Hayden Buckley, Masters champion Hideki Matsuyama, John Rahm (through 17) and Sebastian Munoz (through 14).

Koepka has gone on to win or finish second in six of the last 10 majors which he opened with a score in the 60s.

World number one Dustin Johnson and star Rory McIlroy were both through 17 holes when play was called for the day.

Johnson had mixed a birdie with a bogey, while four-time major champion and 2011 U.S. Open winner McIlroy had an eventful start with three bogeys and four birdies.

Defending champion Bryson DeChambeau and his bid for back-to-back trophies started with a two-over-par 73.

American star Mickelson ended the round two shots worse off than DeChambeau following his forgettable 75.

Mickelson, who became the oldest major winner when he clinched the US PGA Championship last month, finished with five bogeys, including back-to-back on the front nine.