Cinci stroll for Serena

World No 1 Serena Williams crushed Serbian Jelena Jankovic 6-1 6-3 to reach the semi-finals of the Southern and Western Open in Cincinnati.

Williams, who lost to elder sister Venus in the semi-finals in Montreal last week, needed just 58 minutes to beat the eighth seed. She will play Caroline Wozniacki of Denmark in Saturday's semi-finals.

Jankovic caused Williams a lot of problems at one point in the American's career. Prior to Williams' year-long injury lay-off in 2010/11, the pair were tied at four wins apiece head-to-head.

In their five meetings since, however, Williams has emerged victorious on every occasion and the trend continued in Cincinnati.

She stormed through the first set in just 25 minutes and then reeled off five more games in a row in the second before booking her spot in the semi-finals with back-to-back aces in the final game.

"She's beaten me several times, so I knew today I just had to be focused and do the best I could," Williams told the WTA Tour website.

"It didn't seem fast. I was just trying my best. And she played some great points. I was just trying to not make many errors, stay focused and do the best that I could.

"I had some unbelievable fans in the back who were totally helping me out, too."

Despite Williams' long and impressive list of achievements, the title in Cincinnati has so far eluded her. She now finds herself just two wins away from finally crossing the Southern and Western Open off her list.

Williams will face Wozniacki in the last four after the Dane caused a minor upset by defeating fourth seed Agnieszka Radwanska 6-4 7-6 (7-5).