ZURICH, Switzerland — Venus Williams rallied from a set down to beat Ana Ivanovic 4-6, 6-3, 6-4 today in the Zurich Open semifinals.

Williams will face Flavia Pennetta in Sunday's final, after the Italian beat Spain's Anabel Medina Garrigues 6-3, 7-6 (6) in an earlier match.

Pennetta is 3-1 against the 28-year-old American and beat her in Moscow last week.

The third-seeded Williams is looking for her second singles title of the year, after winning Wimbledon, as she tries to secure a place in the season-ending WTA Tour championship in Doha, Qatar, next month.

Williams struggled with her serve in the first set and double-faulted to give Ivanovic a break to go up 4-3.

In the decisive set, Williams broke to go up 4-3 when Ivanovic netted a forehand, but the American missed three match points during her opponent's next service game — with Ivanovic's forehand volley rolling on the net cord before dropping in on the third.

Williams served out the match in the next game.

Pennetta, who upset top-ranked Jelena Jankovic in the second round Thursday, reached her fourth final of the year, despite trailing 3-1 in the first set.

She then found her forehand power and won five straight games, including three breaks of serve, to take the set.

Medina Garrigues, ranked 30th, led 3-1 again in the second but Pennetta broke to even the set at 3-3.

The 26-year-old Spaniard couldn't serve out the set at 6-5 as Pennetta forced a tiebreaker.

Pennetta survived a set point and converted her first match point as Medina Garrigues hit a driving forehand volley long.

She said it did not matter that she beat Williams in Moscow last week

"Here it is another tournament," Pennetta said. "Last week I lost against Jankovic and this week I won so everything can happen."

The Italian has won two tournaments this year, at Vina Del Mar, Chile, in February and Acapulco, Mexico, in March.