Australian third seed Samantha Stosur has overcome a spirited fightback by Romania’s Monica Niculescu to advance to her first semi-final of the year at the WTA Qatar Open.

Stosur, the reigning US Open champion, won 6-2 2-6 6-3 in a little short of two hours on Friday after totally losing her momentum in the second set and surviving a tough spell in the third when Niculescu took three games in a row to level at 3-3.

Niculescu had a wonderful opportunity to break Stosur in the seventh game of the decider when she was leading 30-0, but sent an easy volley long after a lengthy rally to give the Australian the opening she was looking for.

Stosur, the world’s fifth-ranked player, latched onto it gratefully to hold her serve, and won the next two games in a hurry.

“It was an up-and-down match for both of us,” said Stosur.

“I was able to pick up my game at the end of it. I believed in myself.”