Fourth-ranked Rory McIlroy took confidence from a strong performance off the tees in Thursday's opening round of the US Open, despite feeling like he might have scored a bit lower.

The four-time major champion from Northern Ireland fired a three-under par 67 at Winged Foot to stand two off the lead on a suburban New York layout when accuracy off the tee and clutch putting were at a premium.

"Putting the ball in play off the tee. That was important today. I did that well for the most part," McIlroy said. "I still missed a few fairways, but I was able to recover from there. I hit a lot of good tee shots.

"It gives me a little more confidence in my game, maybe a little more commitment with my swing off the tee, not guiding it as much, really being able to free-flow and make good, committed swings.

"Hopefully that sets me up to do that over the next few days. I feel like most aspects of my game are a little more under control now than they were say a month ago."

McIlroy went three-under on the par-3 holes in his first major round as a father, daughter Poppy being born just over two weeks ago.

"Had a really good start," McIlroy said. "Played the par-3s really well. Drove the ball better. I put the ball in play much more today than I have done in the previous few weeks. That bodes well. That's what you need to do around here, just keep it in the short stuff."

With three days remaining, McIlroy was satisfied with his start even as he reflected on where he might have lowered his score.

"Could have been a little lower than it was, but at the same time 67 is a really good start," McIlroy said.

"I three-putted for par on six. There was a couple other chances I let slip by, the three-putt for bogey on one. So there was chances there to maybe sneak another two or three out of the round."

A concern for McIlroy had been having first rounds that failed to live up to the three that followed once he looked back at tournament performances.

"Maybe putting myself under a little too much pressure to get off to a good start. First round of a major you're always anxious to play well, and maybe I've overthought it at times," McIlroy said.

"I just went out today and just took what was given to me a little more relaxed and played really nicely."

That solid start, McIlroy said, enables him to worry less about chasing a score and more about constructing a steady round.

"I think at a US Open, if you can get off to a good start, you're not chasing as much. And when you chase on US Open golf courses, that's when you can start to make mistakes and compound your errors," he said.

"To have that sort of cushion, to be a little bit more relaxed about your play, not take on too much, be able to still play conservative golf, I think that's important here.

"For the most part I did drive it well. I hit my irons good. When I got out of position, I tried to just get myself back in position and play from there. I didn't really take on too much."

Conditions were perfect for scoring with greens receptive early and wind down, but McIlroy wasn't wanting to see firmer greens or an effort to toughen the course.

"I wouldn't call it scorable by any stretch of the imagination," he said. "There are a couple of guys that have went a little lower than maybe was expected, but it's not as if the rest of the field are finding it that easy."