Ash Barty has snuffed out a spirited challenge from home hope Lauren Davis to advance to the US Open third round.

Barty needed more than two hours to put the world No.73 away 6-2 7-6 (7-2) in a tense match played under a closed roof on Louis Armstrong Stadium after a rain-marred third day in which most of the schedule was wiped out.

“When I saw it was raining today, I was pretty happy I was on this beautiful court with the roof,” Barty said.

“It’s been an incredible development of this tournament and I’m just looking forward to my next match.”

Unlike her tournament opener against Zarina Diyas – or three of her matches at Cincinnati – where she dropped the first set, Barty jumped out of the blocks on Wednesday night.

Barty barely gave Davis a sniff in the first set, breaking the American on her first service game and then pocketing the set when Davis double-faulted trying to stay in it.

Davis threatened to force a deciding third set after establishing a 5-3 lead in the second but Barty broke back and then turned the screws to lead 6-5.

The French Open champion fashioned three match points on Davis’s next service game but couldn’t convert.

“There were parts of my game that I still want to clean up. There’s always room for improvement every single match that you play,” Barty said afterwards.

Serena Williams was made to work for her victory over teenager Catherine McNally. Photo: Getty

Later on Wednesday (local time), Serena Williams survived a scare from teenage wildcard Catherine McNally to keep alive her hopes of securing a record-tying 24th grand slam title.

Eighth-seeded Williams – who won the first of her six titles at Flushing Meadows two years before her 17-year-old opponent was born – spent the first half of the match trying to find her rhythm but when she did she was off to the races in the 5-7 6-3 6-1 win.

“She really came out and played really well. She showed no fear,” a relieved Williams said.

“She had absolutely nothing to lose and she played like it.”

McNally, competing in only the sixth tour-level event of her career and against the highest-ranked player she has faced, used an old-school serve-and-volley approach along with a lethal slice backhand to unsettle Williams.

So effective was McNally that at one point in the match Williams screamed at her own racquet “Why are you missing?”

“I survived tonight,” said Williams, who made 28 unforced errors.

“I am not too pleased with the way I played at all but it’s OK, I’m alive.”

Up next for Williams will be Taiwan’s Hsieh Su-wei or Czech Karolina Muchova, who were unable to get their match in earlier due to rainy conditions.

Williams is drawn to meet Barty if they progress to the quarter-finals.

First, Barty must win her next match, which will be against 30th-seeded Maria Sakkari or Peng Shuai. They will resume their match on Thursday after their second-round clash was suspended at 1-1 in the opening set.

Wednesday’s US Open win improved Barty’s grand slam record to 16-2 in 2019 and edged the Queenslander to within one win of matching her career-best run in New York from last year.

The only other Australian in action on Wednesday, Alex de Minaur, also had his match delayed by rain.

De Minaur was leading Chilean 31st seed Christian Garin 1-0, with Garin 30-love up on serve, when play was stopped just eight minutes into their match.

De Minaur will also return to finish on Thursday.

-with AAP