Reigning champion Samantha Stosur and third seed Maria Sharapova were easy first-round winners on a rain-interrupted Day 1 at the 2012 U.S. Open.

The seventh-seeded Stosur won her eighth straight match in New York with a brisk 51-minute 6-1, 6-1 pasting of Croat Petra Martic at Arthur Ashe Stadium. Stosur won the first 19 points of the match and fired 10 aces past a helpless Martic. The Aussie lost only four points while serving in the lopsided affair.

Stosur stunned American great Serena Williams in last year's U.S. Open finale to capture her lone career Grand Slam title. The Aussie star was also a French Open runner-up in 2010.

"As soon as I got here, it was just a good feeling and excitement to be back to a city that obviously brought me so much last year," Stosur said.

The 28-year-old Stosur, who has been somewhat disappointing this year, was a first-round loser at the Australian Open in January and Olympic Games last month and lost in the second round at Wimbledon in June.

Sharapova, meanwhile, breezed past Hungarian Melinda Czink 6-2, 6-2. The 2006 U.S. Open champ, Sharapova completed the career Grand Slam earlier this year by winning at Roland Garros.

Ninth-seeded former French Open champ Li Na of China advanced following a more-than-two-hour rain delay with a 6-2, 6-3 handling of Britain's Heather Watson, while 11th-seeded former Wimbledon runner-up Marion Bartoli of France won her 18th straight first-round Grand Slam match by topping American Jamie Hampton 6-3, 7-6 (7-5). Li was a hardcourt titlist in Cincinnati two weeks ago.

In other action involving seeds, No. 15 Czech Lucie Safarova handled American Melanie Oudin 6-4, 6-0, No. 19 Russian Nadia Petrova beat Aussie Jarmila Gajdosova 6-3, 7-6 (7-3) and No. 31 American Varvara Lepchenko outlasted Frenchwoman Mathilde Johansson 6-3, 3-6, 7-5.

Upsets came when Romanian Sorana Cirstea overcame 16th-seeded German Sabine Lisicki 4-6, 6-2, 6-2, Czech Kristyna Pliskova dismissed 18th-seeded German Julia Goerges 7-6 (7-4), 6-1, and Czech Lucie Hradecka doused 27th-seeded Spaniard Anabel Medina Garrigues 6-3, 6-3.

Also advancing were Romanian Simona Halep, Aussie Casey Dellacqua, Georgian Anna Tatishvili, Luxembourg's Mandy Minella, Swiss Romina Oprandi, Spaniard Lourdes Dominguez Lino, and Canadian Aleksandra Wozniak.