By Mark Lamport-Stokes

OAKMONT, Pennsylvania (Reuters) - Having shrugged off the frustration of multiple weather delays at Oakmont Country Club on Thursday, Lee Westwood continued his run of good form by charging into contention at the U.S. Open on Friday.

The English former world number one had four holes to play when he returned to the rain-softened course to complete his marathon opening round and he finished birdie-birdie to card a three-under 67 to sit just one stroke off the early lead.

"It was good," Westwood told reporters after a round highlighted by an eagle at the par-four 14th, four birdies and three bogeys. "I've been playing well. Really looking forward to coming back to Oakmont.

"I had a good experience here the last time, albeit everybody found it tough," he said of the 2007 U.S. Open when he tied for 36th at 18 over par. "I like a challenge, and this golf course is certainly a challenge. It tests you mentally.

"I sort of picked up where I left off at the Masters and the last three weeks I've played. I hit the ball well, a lot of fairways, a lot of greens. I hit it close quite a lot, 26 putts. It's a good way to start this championship."

It was Westwood's best opening round at a U.S. Open in his 17th appearance in the year's second major, and it followed on from his tie for second at the Masters in April.

"I felt confident out there and hit a lot of good shots," said the 43-year-old, who is still seeking his first major title after 18 top-10s in grand slam events over the years.

"I was shaping it both ways, which you need to do in U.S. Opens to get at a lot of the flags. To walk off two under par for those (last) four holes was obviously very satisfying and a great way to finish the round off."

Asked how difficult it had been to stay focused through Thursday's three weather delays, Westwood replied: "In professional golf, you should be able to switch off, switch on, switch off, whenever you can. We're doing that between shots.

"So if you have to switch off for two or three hours ... so be it. It's part of the job a lot of the time. Just got to grin and bear it and get on with it and have another coffee."

(Editing by Larry Fine)