|First round leaderboard|
|-5 H Stenson (Swe), D Johnson (US); -4 P Reed (US); -3 M Kuchar (US), B Martin (US)|
|Selected others: -2 M Warren (Sco), J Day (Aus); -1 P Mickelson (US), MA Jimenez (Spa), C Montgomerie (Sco); Level S Garcia (Spa); +2 R McIlroy (NI), J Rose (Eng), P Casey (Eng), I Poulter (Eng); +3 L Donald (Eng), L Westwood (Eng); +4 G McDowell (NI), J Donaldson (Wal); +10 T Woods (US); +11 R Fowler (US)|
World number one Rory McIlroy bemoaned the Chambers Bay putting surfaces as an opening two-over-par 72 left him seven off the pace at the US Open.
McIlroy, 26, performed well from tee to green but struggled with his putting as he finished seven behind leaders Dustin Johnson and Henrik Stenson.
2010 US Open winner Graeme McDowell is two further back after a 74 while Darren Clarke hit a 77.
Shane Lowry is the leading Irish player after an impressive one-under 69.
McIlroy joined Sergio Garcia and Colin Montgomerie in expressing disappointment at the condition of the Chambers Bay greens.
"They are not the best I have putted on," added the world number one.
Northern Ireland's McIlroy, who missed the cut in both the BMW PGA Championship at Wentworth and the Irish Open at Royal County Down last month, continued: "I should be used to it as the last two tournaments I've played have been just as bad.
"There were a couple of misreads and a couple of bad strokes in there as well.
"It's hard to pick the line and trust it, and then you start making tentative strokes and you are not getting a true roll on the ball. I need to work on that and see if I can figure something out."
The Northern Irishman had two birdies and two bogeys in his opening seven holes and after a run of eight pars, bogeyed two of his last three.
Benign conditions helped the early starters but McIlroy was unable to capitalise on a birdie on the 11th, bogeying the 14th and 15th holes before getting back to level with a birdie on the 16th.
He looked set for a solid opening round but further bogeys on the seventh and ninth holes left him seven off the pace.
McDowell's struggles continued as three front-nine bogeys and a double bogey at the 10th left him on five over although he undid some of the damage by picking up shots at the 14th and 16th.
2011 Open champion Clarke only managed one birdie in a 77 which included six bogeys and two dropped shots at the 10th hole, the first.