Serena Williams has strengthened her claim for a fourth Rogers Cup title by beating Italy's Roberta Vinci to reach the semi-finals..

The American and world number one produced a 6-4 6-3 win in 79 minutes to advance into the last four, where Belinda Bencic or Ana Ivanovic await.

The first set began in nip-and-tuck fashion as all nine games went with serve, but Williams, who led 5-4, pulled out a timely break to draw first blood.

However, world number 53 Vinci hit back with a break of her own to move 2-1 ahead in a gesture which only served to rile Williams, who instantly drew level at 2-2.

The 21-time Grand Slam winner looked on course for another break as a 4-2 lead beckoned, but Vinci recovered from 30-0 down to hold serve.

Nevertheless, the underdog's defiance only delayed the inevitable as Williams won three straight games to progress.