Four-time major champion Phil Mickelson and second-time major starter Billy Horschel remained tied for the lead after the second round of the US Open as yesterday's challengers faded.
But world No 1 Tiger Woods, a 14-time major golf champion chasing the all-time record of 18 majors won by Jack Nicklaus, lurked only four strokes off the pace in a share of 13th with the third round looming overnight.
Woods seeks a record-tying fourth US Open crown but has never won any title when over par after 36 holes and has never won a major crown when he was not leading after 54 holes, making his impending 18 holes even more crucial.
The storm-hit showdown at Merion, thrown off schedule after play was halted for more than four hours on Thursday, continued in perfect conditions yesterday with 73 players making the cut at eight-over-par 148.
Mickelson, a five-time US Open runner-up still chasing the elusive trophy, and fellow American Horschel, who missed the cut at the 2006 US Open in his only prior major start, set the overnight pace at one-under 139 for 36 holes.
England's Luke Donald and Justin Rose, seeking their first major titles, and American Steve Stricker, trying to become the oldest US Open champion at age 46, were also in the clubhouse just one stroke back on 140.
South Africa's Charl Schwartzel, the 2011 Masters winner, was in a pack on 141 that also included Australian John Senden, Belgium's Nicolas Colsaerts and American Hunter Mahan, who was among 67 players to finish his round yesterday.
"I don't think you are really in it until the back nine Sunday," Mahan said.
"The leader is irrelevant. Thinking about the lead or your position is a waste of time because it's a tough course. You're going to make mistakes."
England's Ian Poulter, one off the lead with four holes to finish when the darkness-halted round resumed, stumbled with bogeys at 16 and 18 to finish on 142 alongside Aussie Mathew Goggin and Sweden's Henrik Stenson.
"I'm three off the lead in the US Open, and that's a difference of one hole," Poulter said. "You can make birdie and someone can make double. I'm right in position and right there where I want to be. It's going to be a fun weekend."
Taiwanese amateur Pan Cheng-Tsung was two under for the round and level par overall after nine holes Friday, but bogeys at the par-4 14th and 15th holes and a double bogey at the par-3 17th dropped him back to a 72 to stand on 144.