Americans Coco Gauff and Jessica Pegula off at a canter at Australian Open

Pegula, seeded third behind Iga Swiatek and Ons Jabeur, hit her stride early in the new season by helping the United States win the inaugural United Cup and took less than an hour to see off Jaqueline Cristian 6-0 6-1.

She simply overpowered her Romanian opponent and there were loud cheers from the Margaret Court Arena crowd when Cristian held serve in the second set to avoid the dreaded 'double bagel'.

"It definitely gives me a lot of confidence winning matches like that, knowing I'm playing really focused every single point and not letting any kind of points or games go to waste," said Pegula.

"Definitely first matches are always really tough, especially at a slam, there's so much hype and anxious nerves leading up. So I'm glad it just went very smooth."

Pegula also said she is happy to keep flying under the radar at the Australian Open. Usually, it is the likes of three-time Grand Slam winner Swiatek or Jabeur from Tunisia hogging the headlines in women's tennis.

And that suits Pegula just fine.

"I think girls like Iga or Ons, I feel like maybe their stories are a little bit more, I don't know, grab more attention," said Pegula, the top ranked U.S. woman.

"Ons, for what she's doing for the region she comes from in Africa and all that stuff, and then obviously she made two slam finals as well.

"Iga obviously being younger and bursting onto the scene and winning crazy match win streaks. I guess those maybe grab more attention probably than me."

Pegula's lower profile comes despite being a four-time Grand Slam quarter-finalist, which includes a run to the last eight of the 2022 Australian Open when she was eliminated in straight sets by eventual champion Ash Barty.

"I definitely think I have just kind of been a little bit under the radar, but I don't mind that," she said.

"I think that fits me and my personality as well. I don't think I do too many things to really grab a ton of attention."

Danielle Collins, runner up to Ash Barty at Melbourne Park last year, had an injury timeout for a knee issue before grinding out a 7-5 5-7 6-4 win over Anna Kalinskaya.

"Any time you're on the court playing three-hour matches, you especially want to win, so I just needed to push through the hurdle a little bit," the 13th seeded American said.

"Definitely had a scare there with the injury in the first set but I was able to work through it. I'm just counting my lucky stars there a bit, it really was not a good start for me."

Amanda Anisimova was unable to continue the good start for American women at the first Grand Slam since Serena Williams hung up her racket, the 28th seed tumbling out 6-3 6-4 at the hands of Ukrainian Marta Kostyuk.

With Barty and Williams both retired, and twice champion Naomi Osaka pregnant with her first child, Melbourne Park will almost certainly crown a first-time women's champion this year.

There were convincing early wins on Monday for two former U.S. Open champions who have been unable to build on their Grand Slam success.

Canadian Bianca Andreescu, the 2020 champion at Flushing Meadows, beat Marie Bouzkova 6-2 6-4, while 2021 winner Emma Raducanu made light work of Tamara Korpatsch in a 6-3 6-2 victory.

Briton Raducanu, now 20, will next face teenager Gauff, who came into the year's first Grand Slam on the back of a title win in Auckland and confirmed her good form with a 6-1 6-4 win over Katerina Siniakova on Rod Laver Arena.

Greek sixth seed Maria Sakkari also had a straightforward 6-1 6-4 win over China's Yuan Yue to set up a tie against Russian qualifier Diana Shnaider.

Italian 15th seed Jannik Sinner, a quarter-finalist last year, was the first man to reach the second round, rolling over Briton Kyle Edmund 6-4 6-0 6-2 on John Cain Arena.

Polish 10th seed Hubert Hurkacz joined him with a 7-1(1) 6-2 6-2 win over Spain's Pedro Martinez.