All to play for as round three begins at Erin Hills

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A congested leaderboard and the potential for thunderstorms meant an enthralling day was in prospect at Erin Hills as the final groups prepared to go out in round three of the U.S. Open.

Paul Casey, Brooks Koepka, Brian Harman and Tommy Fleetwood shared the lead on seven under, with Rickie Fowler, Jamie Lovemark and JB Holmes one back.

However, plenty of others were firmly in contention at the start of the penultimate day; only eight shots separated the leaders from those who made the cut on the bubble.

With a host of high-profile stars, including the top three in the world rankings, having missed the cut, the top 18 at the end of round two was made up entirely of players still seeking their first major.

That increased the likelihood of a seventh successive major producing a first-time winner, although the likes of Masters champion Sergio Garcia and Martin Kaymer - who claimed U.S. Open glory in 2014 - were handily placed four off the pace.

Erin Hills was drenched by nearly an inch of rain overnight, but many of those out early on Saturday still found scoring to be difficult.

Louis Oosthuizen did make encouraging progress, though, birdieing four of his first eight holes to join the group tied for 13th at four under, three behind the leading quartet.

Zach Johnson was also four under for the day through 16 holes, lifting him to three under overall, while Jack Maguire proved that fortunes can change in a hurry when he drained an eagle putt from off the green on the par-five first.

Koepka and Fleetwood were due out at 2:18pm local time, with the final pairing of Casey and Harman starting 11 minutes later.