Both players were distracted by an air show in the skies over Melbourne Park to mark Australia Day, and three double faults on Keys' opening serve gifted Pegula the advantage again in set two.

Learner Tien battled through a nosebleed to thrash three-time finalist Daniil Medvedev at the Australian Open on Sunday and make a Grand Slam quarter-final for the first time.

She will play another fast-rising teenager, American Iva Jovic, or Kazakhstan's Yulia Putintseva for a place in the semi-finals.

Extreme heat triggered a suspension of play on outside courts at the Australian Open on Saturday and briefly held up the match involving champion Jannik Sinner before his encounter resumed under a closed roof.

American 18-year-old Iva Jovic pulled off the biggest upset of her young career when she stunned Italian seventh seed Jasmine Paolini 6-2, 7-6(3) at the Australian Open on Friday for her first Grand Slam last-16 appearance.

Six-time Grand Slam winner Carlos Alcaraz was put through his paces by German journeyman Yannick Hanfmann on Wednesday before swatting him aside to book his place in the Australian Open third round.

The world number one saw off the awkward Bai 6-3, 6-1, having threatened at one stage to complete the job in even more express fashion.

The American ninth seed was a bundle of nerves on Rod Laver Arena, but calmed down to clinch a 7-6 (8/6), 6-1 win over Ukraine's Oleksandra Oliynykova.

Gauff started her quest for a maiden Australian Open title with a 6-2 6-3 win over Kamilla Rakhimova.

Aryna Sabalenka warned she was only going to get better as the top seed recovered from a slow start to launch her Australian Open with a straight-sets win on Sunday.

Play was halted during an Australian Open first-round match Sunday when a ball girl fainted as temperatures soared, with players Zeynep Sonmez and Ekaterina Alexandrova rushing to help her.

Alexander Zverev overcame a shaky start before reaching the second round on Sunday's first day of the Australian Open, as top-ranked Carlos Alcaraz and Aryna Sabalenka get set to enter the fray.

Former Wimbledon champion Marketa Vondrousova withdrew from the Australian Open on Sunday after the Czech player said she was dealing with a shoulder injury.

Alcaraz starts his bid for a career Grand Slam, with the Australian Open the only title missing from his collection.

Seven-time Grand Slam champion Venus Williams said Saturday she was "up for the challenge" as she gets set to become the oldest woman to play at the Australian Open at age 45.

The Australian Open will offer a record A$111.5 million ($74.73 million) in prize money this year and while players welcomed the increase, top names like Coco Gauff and Aryna Sabalenka said the push for a bigger payout must continue across the Grand Slams.

Tennis fans in Australia could win A$10 million ($6.71 million) by correctly predicting every match winner at the Australian Open, tournament organisers said on Tuesday.

Aryna Sabalenka beat Karolina Muchova in straight sets to reach her third Brisbane International final in a row on Saturday, a week ahead of the Australian Open.

Aryna Sabalenka said her much-maligned exhibition match against Nick Kyrgios had paid dividends as she demolished Cristina Bucsa on Tuesday to launch her Australian Open preparations.

The winners of the men's and women's singles at the first Grand Slam of the year will each take home Aus$4.15 million (US$2.79 million), up 19 percent from last year's Aus$3.5 million.