Top seed Argentine Juan Martin del Potro progressed to the semifinals of the Sydney International beating Czech veteran Radek Stepanek at the Olympic Park Tennis Center here Thursday.
The World No.5 was forced to battle for more than two hours before seeing off Stepanek, winning 6-4, 3-6, 6-3.
Del Potro will next meet 2008 Sydney champion, Russian Dmitry Tursunov in the semifinal.
Tursunov beat Uzbek Denis Istomin in straight sets 7-6, 6-2.
