Lee Westwood moved into first place in the U.S. Open, as surprise first-round leader Andrew Landry tumbled down the leaderboard on the third morning at Oakmont.
Landry and Westwood - tied second at this year's Masters - were among those to finally begin their second rounds in a weather-affected event on Saturday, the former teeing off as co-leader with Dustin Johnson, who played 36 holes the previous day.
Rounds of 67 and 69 saw Johnson match Landry's score of four under, but the latter soon gave up ground on his return to action as he dropped four shots in three holes from the sixth.
Westwood, however, birdied the first to tie the lead, before picking up another shot at the long fourth to move clear at five under.
Behind Johnson, Scott Piercy and Sergio Garcia - who also finished their second rounds on Friday - remained the nearest challengers, two off the pace.
Bubba Watson, Shane Lowry, and Russell Knox were all under par for the tournament as they tackled the front nine.
An opening bogey saw Jordan Spieth drop back to three over, but the reigning champion made immediate amends by birdieing the next.
World number three Rory McIlroy made an excellent start in his bid to make rounds three and four, birdieing the 10th - his first hole - and 12th to get back to five over.
The projected cut stood at seven over on a challenging course expected to yield a winning score somewhere around par.
Hideki Matsuyama (+12) and former U.S. Open champions Ernie Els (+10) and Retief Goosen (+10) were among those set to miss the weekend.
Meanwhile, Henrik Stenson withdrew on Saturday morning, having followed up his opening 69 by shooting 10 over for 16 holes in his second round on Friday.