“Obviously winning is fun but winning close matches (is) rewarding,” Williams said.
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.
Williams said her game plan Sunday will be to cut out mistakes.
“I made so many errors in Moscow,” she said. “I think she has played well all the times we have played.”
Pennetta said it did not matter that she beat Williams last time.
“Here it is another tournament,” Pennetta said. “Last week I lost against (Jelena) Jankovic and this week I won so everything can happen.”
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 said Ivanovic was an aggressive opponent.
“When she plays me she is going for everything,” Williams said. “Sometimes it is tough to get a rhythm.”
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.
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 the top-ranked Jankovic in the second round Thursday, reached her fourth final of the year.
She was trailing 3-1 in the first set, then 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.
Pennetta survived a set point in the tiebreaker and converted her first match point as Medina Garrigues hit a driving forehand volley long.
The 26-year-old Italian has won two tournaments this year, at Vina Del Mar, Chile, in February and Acapulco, Mexico, in March.
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