Serena survives Wozniacki test

World No 1 Serena Williams claimed a hard-fought 4-6 7-5 7-5 victory over Caroline Wozniacki on Friday to reach the semi-finals of the Rogers Cup in Montreal.

Williams, who lifted her third Canadian crown last year when the tournament was held in Toronto, battled back from a set and a break down to stretch her career head-to-head record over the 13th-ranked Dane to 7-1.

Wozniacki, a former world No 1 who is seeded 11th, claimed her only victory over the US star in the quarter-finals at Miami in 2012.

In Saturday's semi-finals, Williams could find herself across the net from her sister Venus, who was due to play Spain's Carla Suarez Navarro.

Suarez Navarro is coming off a third-round upset of French Open champion Maria Sharapova.

As she has in many of her recent matches, Williams made a slovenly start against Wozniacki and the Dane was soon up 6-4 4-2.

With the aid of an improved serve -- which yielded a total of 15 aces in the match, Williams began to assert herself.

Wozniacki twice recovered a break in the third set before Williams finally closed out the match after two hours and 41 minutes.