We're down to 32 players at the US Women's Amateur - and two of them are Australian.

Defending champion Gabi Ruffels and rising Queenslander Emily Mahar progressed at Woodmont Country Club in Maryland, the latter true to her word about seedings being "nothing more than a number" in knocking out one of the favourites.

Ruffels, a member at Victoria Golf Club in Melbourne, was twice headed by South African Kajal Mistry who made birdies on both early par-5s.

But, just as she did so successfully in Mississippi last year, Ruffels - again the sixth seed - didn't panic and forged her way to the lead with a string of important pars.

Her lone bogey on the 12th enabled the No.59 seed to momentarily square the match again, but the Aussie responded with birdies on the 13th and 15th to go 3-up, meaning a par on the par-3 16th was enough for a 3&2 victory.

"It was a little bit of a shaky start," said Ruffels, a junior at the University of Southern California.

"It took me a while to kind of get into it, but I was really happy with the way I finished ... especially the 16th where I hit a hybrid to about 15 feet to end the match."

Mahar has scarcely made a putt of note to date this week, so when it came crunch time today, she turned to a different club to make her mark against Alabama's Micheala Williams.

And it proved decisive.

The pair had been close until pars on the 10th and 11th were enough for the Keperra member to go 2-up.

Williams, a recent graduate from the University of Tennessee, closed within one with a great birdie on the short 16th to set up a tense finish.

And when both players found trouble off the downwind 18th tee, all results were still on the cards.

But after both laid up, Mahar took matters into her own hands and almost holed a spectacular sand wedge from 53 yards, drawing a concession from the American, the second highest seed to fall on day one of match play.

"I'd three-putted on the 17th when I could have closed it out, so that was frustrating to open the door after she'd missed the fairway," Mahar said.

"Then my tee shot on the 18th carried the bunker by an inch and I had no stance for my second, so that made it more difficult than I'd have liked.

"We both had to lay up, but then I hit one to three inches ... I thought it was going in.

"And yeah, hers rolled through and she conceded. It was great."

Virginia Tech senior Mahar, who has represented Australia twice in competitions in North America, said she'd been happy with her start, even though her opening birdie was only good for a half.

"I knew she was good and hot with the putter, so I had to do something and we both started really well," she said. "But by the back nine, we both fell apart a bit, so it flipped. It was just frustrating that I couldn't take advantage of doors she opened.

"But my game was pretty solid and even though I wasn't making the birdies I wanted to, but she was missing more fairways and greens so I just stuck to my game plan of making pars ... and that was enough."

Fellow Queenslander Kirsty Hodgkins, a University of Colorado senior, was the lone Australian casualty, falling 4&2 to Alyaa Abdulghany.

Redcliffe member Hodgkins, the 52nd seed, simply couldn't make a birdie and get the honour from the more consistent Malaysian, who made one of her own to close out the match on the 16th green.

After losing a day's play earlier this week because of Hurricane Isaias, the USGA will play two rounds of match play in each of the next two days to catch up and ensure a Sunday (local) finish.

Ruffels will face Chinese No.38 seed and last year's US Junior Girls' champion Lei Ye first up tomorrow, with Mahar to play South African No.24 seed Kaleigh Telfer.