World number one Serena Williams roared to a straight-sets win over Serbian Jelena Jankovic to move into the semi-finals at the Western & Southern Open.

Williams, bidding for her first title at the Ohio hardcourt tournament, romped to a 6-1, 6-3 victory in just 58 minutes.

"She's beaten me several times, so I knew today I just had to be focused and do the best I could," Williams said after claiming her 10th win in 14 matches against Jankovic.

"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."

Williams, unsuccessful in five previous attempts at Cincinnati, will face Dane Caroline Wozniacki on Saturday for a chance to play for Sunday's title.

The 12th-seeded Wozniacki upended fourth seed Agnieszka Radwanska of Poland 6-4, 7-6.

The other semi-final will match Russian Maria Sharapova, who edged second-seed Simona Halep, against former world number one Ana Ivanovic of Serbia.

Sharapova, seeded fifth, outlasted Romanian Halep 3-6, 6-4, 6-4 and Ivanovic beat Ukrainian Elina Svitolina 6-2 6-3.

Source: Reuters