China's Li Na serves during the quarterfinal match of women's singles against Andrea Petkovic of Germany at the Australian Open tennis tournament in Melbourne, Australia, Jan. 25, 2011. (Xinhua/Meng Yongmin)

MELBOURNE, Australia, Jan. 25 (Xinhua) -- China's top player Li Na cruised into the semifinals at the Australian Open for a second consecutive time without conceding a single set here after ousting German rising star Andrea Petkovic in the women's singles quarterfinals.

Li, seeded 9th, came from behind to won both sets 6-2, 6-4 in 80 minutes, extending her winning streak to 10 matches in the new season.