Australian Karrie Webb has no explanation for one of the worst performances of her career, a 12-over-par 83 in the opening round of the US Women's Open.

"I have no idea what happened," a shell-shocked Webb said after her shocking performance on the same Pine Needles course where she won the Open six years ago.

"It was not what I expected. It was a terrible round, probably one of the worst of my career."

She denied being sick or injured, continuing: "I don't make any excuses. I'm not one of those players."

Webb's day got off to a poor start and never got any better.

She bogeyed four of her first five holes, was six over at the turn, and dropped another six shots coming home.

Her card revealed seven pars, 10 bogeys and one double bogey and she was particularly poor on the greens, taking 37 putts.

Seventeen-year-old Michelle Wie fared little better with an 82, while Brazilian Angela Park led on three-under 68 with half the field back in the clubhouse.

Park was two strokes clear of a group of six players, with LPGA money leader Lorena Ochoa three shots back after a late double bogey.

Katherine Hull headed the small Australian contingent on one-over 72, one stroke better than Wendy Doolan, while Rachel Hetherington shot 78.

Queenslander Hull had few complaints about her performance: "I'm very happy with it," she said.

"I missed a couple of short putts and made one double (bogey) but everything else was really good.

"You can go low out here, but you've got to be putting exceptionally well. I don't think this course is going to let that happen four days in a row."

Hull's double bogey came at the par-four seventh, where her five-wood approach shot trickled over the raised green and tumbled down the slope into wet grass.

"I thought I hit it okay, but it came up short, so I chipped it again and then two-putted," she said.

"It's unfortunate, because I hit a great shot in there and it didn't stop."

Leader Park is a citizen of the world, born in Brazil of Korean parents, before moving to California at the age of eight.

"When people ask me are you Brazilian, Korean, American, I think I'm three of them all mixed up together," said the 18-year-old.

She made a great start on a languid morning, picking up four strokes on the easier front nine, before negotiating the back nine with eight pars and a bogey.

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