Rory McIlroy heads into the weekend at the U.S. Open full of confidence after overcoming a back-nine wobble during his second round at Pebble Beach.

After an opening 68 in what he described as benign conditions, the four-time major champion moved to within a shot of the lead at one stage on Friday following a birdie at the 11th hole.

However, McIlroy bogeyed the 13th after finding a bunker with his approach to the green and worse was to come at the next hole, starting with a poorly judged wedge shot that spun back off the green.

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A fluffed chip then found sand, eventually leading to a double-bogey seven, but back-to-back birdies at the next two holes saw him recover to sign for a 69.

His five-under total at the halfway stage of the year's third major leaves him four shots behind Gary Woodland, though McIlroy is delighted with his form following the victory at the Canadian Open last week.

Asked in his press conference if this was as good as he had felt going into the weekend at a major in some time, he replied: "Yeah, I would think so.

"Carnoustie (at The Open) last year I was right up there. I played really solid golf and had a chance on Sunday.

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"But coming off the back of a win last week and having another win this year, as well, and just the consistency that I've shown, it's the best I've felt about my game in a while for sure."

The 30-year-old admitted his desire to reach the top of the leaderboard proved costly, particularly as an aggressive approach at 13 and 14 was not in keeping with the plan to play it safe.

"It was very important to do all that hard work over the first 12 holes, and then to lose it in two holes - at 13 and 14 - was disappointing," McIlroy said.

"At 13, I wasn't disciplined enough with my second shot. I was trying to hit something into that back right corner of the green when I've really been preaching middle of the greens all week.

"I was feeling good about myself, six under par, and felt like I could squeeze a couple more out of the round, the last couple of holes, and maybe get the lead going into the weekend. I bogeyed that (13), which is fine, you're going to make some bogeys around here.

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"But it was just the wedge shot on 14. I hit a club that I knew could pitch pin-high, but probably not very much further than pin-high, and then anything right of that pin, pitching there is going to come off the green.

"I probably missed by four or five yards right of where I needed to. And it came back down the hill, and then you're in an awkward spot, you're trying to play a very precise shot to get it close to the hole to save your par, and that didn't go to plan.

"It just sort of compounded the error with another error, which you never really want to do."