World number eight Li Na needed a tie break to grab the first set against Czech Lucie Safarova but got a quick early break to clinch a 7-6 6-4 victory.

World number five Sam Stosur cruised into the Stuttgart clay court tournament second round on Tuesday with a 6-2 6-2 win over China's Shuai Peng to set up a clash with last year's winner Julia Goerges.

German Goerges, who beat Australian Stosur in the last four en route to the Stuttgart title in 2011, was made to battle a lot harder by Russian Anastasia Pavlyuchenkova before edging past the world number 23 5-7 6-3 6-4.

"It is normal if I come here as defending champion," Goerges told reporters. "Of course there will be expectations and the pressure is on you. I need to improve my game."

Fellow German Andrea Petkovic crowned her comeback on the tour after more than three months out with a back injury with a confidence-boosting 6-1 6-4 victory against wild card Kristina Barrois to set up a second round clash with world number one Victoria Azarenka.

World number seven Marion Bartoli also moved into the second round with a trouble-free win over Czech Iveta Benesova.

Former Wimbledon finalist Bartoli pinned the Czech back with a barrage of groundstrokes and got the first break to lead 3-2 in the first before breaking again to clinch the set with a powerful two-handed backhand down the line.

Qualifier Benesova broke straight back in the first game of the second set but Bartoli upped her game again to ease home.