Australia won promotion to the Fed Cup World Group on Sunday after US Open champion Samantha Stosur gave her team an unassailable lead over Germany in their play-off.

Stosur, ranked fifth in the world, needed 74 minutes to see off Andrea Petkovic, ranked 11th, for a 6-4, 6-1 victory in the third singles rubber which put Australia 3-0 up to settle the promotion/relegation tie.

Angelique Kerber got Germany's first win of the weekend when she beat Fed Cup debutant Olivia Rogowska 6-3, 6-3 in the fourth rubber.

Petkovic and Julia Goerges then combined to enjoy a 6-3, 6-4 victory over Australia's Casey Dellacqua and Jarmila Gajdosova in just 67 minutes to take the fifth and final rubber.

Defeat means Germany will drop to World Group II, while Australia will join the eight-team elite top-tier next season.

Stosur said she was happy with her victory over Petkovic, who played her first match since January having taken time off to heal a persistent back injury.

"I think the difference was that she couldn't hold on to her service games," said Stosur.

"It was crucial that I could break Andrea and it was obvious that she was nervous when it came to the big points.

"She appeared to be a little rusty which is more than normal, when you come back after having not been on the court for more than three months.

"On paper, the Germans had the stronger team so for us this was not easy. I felt very comfortable on the court."

The German admitted she expected more from her comeback.

"Of course, I expected a win, I always do," said Petkovic. "I was very hectic at times and I made the wrong decisions. I felt a bit like a headless chicken on the court at times.

"I feel 1000 percent fit and I am completely pain-free. We are now in World Group II I don't care where or who we will now play.

"This doesn't mean much for the group or my comeback, we are a tight group and we want to win the title."

It was Stosur's second victory of the weekend after she also saw off Kerber 7-6 (7/1), 6-4 in Saturday's opening rubber.

Gajdosova, 50th in the world, then blasted Goerges, ranked 16, 6-4, 6-4 to give the guests a 2-0 lead going into Sunday.