World number one Ashleigh Barty celebrated her 25th birthday by fighting back to beat Elina Svitolina in the semi-finals of the WTA clay-court tournament in Stuttgart on Saturday.

Despite losing the first set in just a over half an hour, Barty hit back to seal a 4-6, 7-6 (7/5), 6-2 win over the Ukrainian fourth seed.

The Australian will meet either second-seed Simona Halep or Aryna Sabalenka in Sunday's final.

"It's important to believe. Regardless of the score, I always try and find the right way," said Barty, who also lost the opening set of Friday's quarter-final against Karolina Pliskova.

"She is one of the best competitors on the tour, so I knew it would be a very hard fought match and the margins would decide it," Barty added before being presented with a bouquet of flowers with "Happy Birthday" played over the arena's sound system.

Barty had little time to celebrate the win or her birthday as she had to partner Jennifer Brady against Vivian Heisen and Wang Yafan in the doubles semi-final.

However, the Australian was seeking no sympathy despite the quick turnaround.

"I love to play tennis and I love to compete, so to do it on my birthday is even more special," added Barty.