Koepka and Fowler pull clear at Erin Hills

Getty Images

Brooks Koepka charged to the top of the U.S. Open leaderboard, but Rickie Fowler was able to respond as the duo pulled clear of the field in the latter half of Friday's second round at Erin Hills.

Fowler had led by one overnight courtesy of a stunning 65 and, although he was joined on seven under by Paul Casey before beginning his second round, the world number nine improved his position with a birdie at the second.

Despite that strong start, Fowler found himself in second place when Koepka - who began the tournament with a 67 - birdied four of his first seven holes after starting on the back nine to reach nine under.

Undaunted, Fowler responded with a mammoth 51-foot putt for birdie on the eighth to reclaim a share of the lead.

Casey had earlier gone round in 71, a run of five successive birdies enabling him to recover spectacularly from a triple-bogey eight on the long 14th.

Another Englishman, Tommy Fleetwood, was three off the lead at six under after nine holes of his second round, with Xander Schauffele, amateur Cameron Champ, Kim Si-woo, Brian Harman and JB Holmes one further back.

The hottest man on the course was unquestionably Hideki Matsuyama, who bounced back from his first-round 74 by birdieing six of his first eight holes on Friday to sit five off the lead.

Rory McIlroy and Jason Day were sure to miss the cut after reaching the clubhouse on five and 10 over respectively, but world number one Dustin Johnson boosted his hopes of making the weekend by clawing his way back to one over for the tournament through five holes.

Johnson was playing alongside Jordan Spieth, who was also two under for the day after five and one under overall.