Reigning US Open champion Samantha Stosur began her title defense with a 6-1, 6-1 victory over Croatia's Petra Martic on Monday before rain halted the first day of play at the Grand Slam showdown. Only four matches were completed on the Flushing Meadows hardcourts before showers arrived, a nagging reminder that the men's final has been played a day late for the past four years as a result of downpours in the fortnight. World number ones Roger Federer and Victoria Azarenka were scheduled for later matches on the first day of the fortnight with Andy Murray, Maria Sharapova and Kim Clijsters also booked in for Arthur Ashe Stadium. Seventh-seed Stosur, seking her first title since upsetting Serena Williams in last year's US Open final, fired 10 aces to advance in 51 minutes on the same Ashe Stadium court where she hoisted the trophy a year ago. "It was great to get out there again," Stosur said. "I felt like I was ready to go. It was a good start. I certainly won't complain about being out there. I'm really happy with the way I played." Stosur, connecting on 69 percent of her first serves without facing a break point, began the match by winning the first 19 points in a row before a double fault ended her bid for a golden set."I knew at 4-0, 40-0 that I hadn't missed a point and the match had been going pretty quick," Stosur said. "It did pop into my head for a split second. Then I hit the double fault and it was erased and I was quickly on with the next point. "It was 19 points in a row. You knew you were going to lose one at some point. It's just the way it goes." Stosur, a semi-finalist at the French Open, made a first-round exit from the Australian Open and the Olympics but avoided joining Svetlana Kuznetsova as the only US Open defending women's champion to lose in the first round. "First round you are always going to have a little bit of nerves," she said. "I felt prepared the best I could. I had done everything I could. The way I felt going into it, I felt pretty relaxed." The 28-year-old from Brisbane will face a qualifier in round two -- either Swiss Stefanie Voegele or Romania's Edina Gallovits-Hall. Aussie Casey Dellacqua advanced in 69 minutes with a 6-2, 6-3 victory over Ukrainian qualifier Lesia Tsurenko. She will face Chinese ninth seed Li Na or Britain's Heather Watson next. Georgia's Anna Tatishvili reached the second round by eliminating France's Stephanie Foretz Gacon 6-2, 6-0 and Czech Lucie Hradecka ousted Spanish 27th seed Anabel Medina Garrigues 6-3, 6-3, before the showers struck.