PARIS - Defending champion Serena Williams survived a fright as she labored into the semi-finals of the French Open with a 5-7 6-4 6-1 victory against Kazakh Yulia Putintseva on Thursday.

The world number one, who will take on Swiss eighth seed Timea Bacsinszky or Dutchwoman Kiki Bertens for a place in Saturday's final, made a mess of numerous routine shots as her opponent took the opening set having made only one unforced error.

The American survived two break points at 4-4 in the second set, which she eventually won when world number 60 Putintseva served a double fault.

The momentum had swung Williams's way and the American crushed Putintseva in the decider, wrapping it up on her fourth match point with an unreturnable serve.