Serena Williams overcame Elina Svitolina in their Western and Southern Open semi-final, setting up a meeting with Simona Halep.

World number one and defending champion Williams had to fight for her 6-4 6-3 victory over the talented Ukrainian.

Williams served nine aces and eight double faults and Svitolina managed to break the powerful American twice.

But the 21-time grand slam champion eventually claimed victory in one hour, 27 minutes in Cincinnati on Saturday.

Svitolina showed no signs of early nerves as she broke in the opening game but Williams was level at 3-3 when the 20-year-old sent a cross-court forehand wide at 0-40.

Serving to stay in the set at 4-5, Svitolina was again broken to love – this time netting a forehand.

Williams coughed up a break at 3-1 up in the second set but restored it on her way to seeing out the victory.

Sunday will mark the 33-year-old's 69th WTA final as she looks for a fifth title this year, having won the Australian and French Opens, Wimbledon and the Miami Masters.

Williams has won 14 straight finals, with her last defeat coming in Cincinnati in 2013.

Awaiting her is Simona Halep after the Romanian cruised past Jelena Jankovic 6-1 6-2.

It took 68 minutes but Halep controlled the contest from the moment she went 2-1 up in the first set.

For Halep, the final is the 19th of her career and fifth of the year, having also been runner-up at the Rogers Cup in Toronto.