Kevin Na and Northern Ireland's Graeme McDowell each fired two-under-par 68s to share a one-stroke lead midway thorugh the first round of the US Open.Photo by: Robert Galbraith/Reuters

Pinehurst, United States – South Korean-born American Kevin Na and Northern Ireland's Graeme McDowell each fired two-under-par 68s to share a one-stroke lead midway thorugh the first round of the US Open.

McDowell, the 2010 US Open winner, and Na, who only made the field by cracking the world rankings top 60 four days ago, each eagled the par-5 fifth to pick up at least a stroke on most of the field.

“I clipped it just perfect, right in the center,” Na said after chipping in for his eagle.

Moist conditions made turtle-backed greens receptive early and gave morning starters a bit of an edge on a later group that included world number one Adam Scott and Masters winner Bubba Watson.

“That was an unexpected eagle opportunity,” McDowell said of his 12-foot uphill putt. “I wasn't expecting it to be quite that receptive. Certainly got fortunate with the draw this morning.”

In the clubhouse sharing third on 69 were Japan's Hideki Matsuyama, Sweden's Henrik Stenson and Americans Brandt Snedeker, Matt Kuchar, Brendon Todd and Jordan Spieth.

“Putting was the strong part of my game today,” Matsuyama said through a translator. “This is really a difficult, demanding course. It was difficult to hit the greens in regulation with the undulations.”

Spieth's bogey at the ninth hole – his last – cost him a share of the lead.

“A tough three-putt on my last hole but all in all, under par at the US Open, I would take it all four rounds,” Spieth said. “All in all a solid day. I'm very pleased with the start.”

Spieth, Matsuyama and Rickie Fowler played together in a young stars trio that carries great expectations.

“We're trying to take some of the majors away from these old guys,” said Fowler.

Reigning British Open champion Phil Mickelson, a six-time US Open runner-up trying for a win to complete a career grand slam, opened on 70.

“I putted OK,” Mickelson said. “I didn't give any away on the short ones but I didn't make any of those I needed from 15 to 20

feet to have a really good round.”

The US left-hander, who turns 44 on Monday, had little reaction to a report federal investigators looking into his links to insider stock exchange trading say they do not plan to file charges against him.

“It hasn't affected my performance. It hasn't been weighing on my mind,” said Mickelson. “I haven't done anything wrong. I'm willing to help out in the investigation any way I can.”

Rory McIlroy birdied the 18th from 10 feet to finish on 71, the same score as British 19-year-old amateur Matthew Fitzpatrick, the 2013 US Amateur winner who turns professional next week.

“I stayed patient and got rewarded with a birdie at 18,” McIlroy said. “It was a grind out there at times but to shoot plus-one was a solid day.

“I just have to work on my speeds on the greens. Content? Definitely. I'm only three off the lead and it's only going to get firmer.”

Defending champion Justin Rose of England opened on 72.

“I drove the ball really well. Putting felt comfortable. My short game was very poor,” Rose said. “Just have to work on chipping and putts. I've got to play some great golf the rest of the week but you pretty much have to do that.”

Fowler fired a 70 while wearing knickerbockers in a one-day tribute to the late Payne Stewart, who won the 1999 US Open at Pinehurst and wore them as a trademark.

“I loved watching him play and to hear how much he was loved,” Fowler said of Stewart, recalling his tears as a schoolboy when he learned Stewart had died in a 1999 plane crash.

“It was cool to give a little tribute, definitely a special day.” – Sapa-AFP