Olympic's Lake Course has been a brute for the players at this week's U.S. Open but Casey Wittenberg took advantage of relatively soft early conditions on Saturday to prove the hilly layout can be tamed.

The 27-year-old American, who had missed the cut in his three previous U.S. Opens, eagled the drivable par-four seventh hole on the way to a three-under 67 to vault up the third round leaderboard.

"I drove the ball great," Wittenberg told reporters after birdies on the last two holes gave him a five-over total of 215.

"I put it in play and the greens were fairly receptive being early in the morning and I was fortunate enough to wiggle in some putts.

"It's a hard golf course," the American said of a firm and fast-running layout that played to an average of 74.487 over the first two rounds, nearly four-and-a-half strokes above par.

Wittenberg, who had opened with scores of 71 and 77 in the year's second major, was delighted to tee off in the sixth pairing of the day.

"The greens were definitely softer today than they were even yesterday," he said.

"If you hit good iron shots it's not overly long so if you can put the ball in the fairway, which is task, you can have opportunities to make birdies.

"Today I hit the ball closer to the hole. Maybe I played a little bit more aggressive from the fairway and it gave me a few better looks, to be honest."

Wittenberg sank a 15-footer to birdie the par-four fourth and, after bogeying the tricky sixth, he drove the green at the 268-yard seventh, his ball eventually settling 20 feet from the pin.

"I made a good putt for eagle there and that kind of got me going," he smiled.

After parring the next nine holes, Wittenberg sank a lightning-fast birdie putt at the par-five 17th, then ended his round with a 20-footer to birdie the 18th.

His day's work was over before overnight leaders Tiger Woods, Jim Furyk and David Toms teed off at the opening hole and Wittenberg predicted conditions would become much more difficult in the afternoon sunshine.

"There are a lot of front pin placements out there and it's hard to get to those front pin placements when it gets a little crusty in the afternoons," he said.

"I'm sure with the sun being out and everybody walking on those greens it's going to be a challenge."

(Editing by Julian Linden)