Juan Martin del Potro battles past Dmitry Tursunov

Seventh seed Juan Martin del Potro overcame a stern challenge from Russia's Dmitry Tursunov to reach the semi-finals of the Cincinnati Open on Friday.

The 2009 US Open champion needed just one break of serve to take a tight opening set 6-4.

Roles were then reversed, as Tursunov began to dominate on his own serve and capitalised on a slopping service game from the Argentinean to win the second set 6-3.

However, Del Potro found another gear in the deciding set, winning 37 of 61 points and eventually cruising to a 6-1 success.

He will now face either Novak Djokovic or John Isner in the last four.