The sometime shaky forehand was on the fritz; the nagging knees pained her; she couldn't find her big serve for stretches; the court conditions steamed like a cauldron that made keeping her grip a slippery proposition and that familiar face on the opposite side of the net was playing with the consistency that can be downright annoying.

Yet through it all, Venus Williams, who has confronted all challenges with the calm disposition of a woman detached from the elements and determined to defend, showed little signs of stress.

Riding timely serving and a daring down-the-line forehand approach, the defending Doha champion rallied to reach her second straight Sony Ericsson Championships final, scoring a 5-7, 6-3, 6-4 over Jelena Jankovic at the Khalifa Tennis Complex.

It will be an all-Williams sisters final on Sunday.

Sister Serena held a 6-4, 0-1 advantage over Caroline Wozniacki when the US Open finalist retired with a left abdominal strain. Wozniacki was the third woman to retire from the eight-player, round-robin event. World No. 1 Dinara Safina retired after two games of her opening match with Jankovic. Victoria Azarenka retired from her match with Agnieszka Radwanska citing cramps on Thursday.

"It feels great to be back in the final," Venus said. "In the first set, I couldn't feel the ball. So just coming back from seeing I could not get a ball in against such a consistent player like Jelena is great."

Williams took treatment for her knee during the match and has shown her resilience in roaring back from three-set losses to Elena Dementieva and sister Serena, in a match where Venus held a match point, to return to the final.

"This is my last tournament of the year so I'm giving it 1000 percent," said Williams, who is scheduled to partner Serena in today's doubles semifinal. "You know, I'm doing the best I can right now."

In one of the most competitive — and highest quality clashes — the sisters have ever played against each other, Serena Williams saved a match point in the third set to subdue older sister Venus, 5-7, 6-4, 7-6(4), in a two hour, 41-minute slugfest in Venus' second round-robin match of the week.

It marked just the third time in 22 meetings between the Williams sisters that they played a third-set tie breaker to decide a match. Serena holds a 12-10 edge over Venus in their head-to-head series.

Today, the seventh-ranked Venus battled back from a 0-2 final-set deficit, winning six of the last eight games to outduel Jankovic.

Scattering an unsightly forehand near the back wall, Williams surrrendered serve to fall behind 0-2 in the decisive set. Shrugging off a sloppy stretch that saw her squander a 40-15 lead and lose eight straight points, Williams came right back and broke with a slick backhand volley for 1-2.

In the fifth game, Williams began to press her advantage and Jankovic blinked. Driving the ball deeper into the court, Williams earned triple break point on a Jankovic double fault. Stepping inside the baseline, she cracked a crosscourt forehand winner to break for 3-2.

The lead proved to be fleeting when Williams fell into a 0-40 hole then, could do little but watch in dismay as Jankovic squeezed a backhand pass up the line inside the sideline to break back for 3-all.

Tension continued to forgo its customary costume and haunt the server as the Serbian sent a forehand wide to drop serve and fall behind 3-4.

Sweat cascading off her shoulders, a revived Williams wasted no time in consolidating the break, administering a love hold to earn a 5-3 advantage.

The pivotal point of the second set came with Jankovic holding triple break point at 0-40 at 2-all. Had she converted one of the break points, the Belgrade baseliner would have been three games from the final, but Williams lifted her level of play.

Jankovic ripped a running forehand approach that pushed Williams wide into the doubles ally. Applying her expansive reach, she flicked a forehand lob winner to earn game point before slamming a swing forehand volley that helped her hold for 3-2.

In the sixth game, Jankovic saved a break point, but Williams blasted a backhand winner down the line to earn a second straight break point. Sending a short second serve into the box, Jankovic erased the break point on a Williams error. A wayward lob from the Serbian gave Williams a third break point. This time, Williams was waiting for the inevitable: the shot to her forehand. Sitting on that shot she stayed line and lined a forehand winner to break for 4-2.

Crushing a series of first serves, Williams delivered a convincing love hold to consolidate for 5-2. Two games later, Williams sliced an ace out wide, her third of the set, in winning her eighth consecutive point on serve to collect the second set, 6-3.

Venus committed only nine unforced errors in the second set, in marked contrast to periods of patchy play she displayed in the opening set.

Trailing 1-3 in the first set, Williams held at 15 then broke back to level the opening set.

At 3-3, 30-all, Williams' woes on the forehand side took shape as she sent a forehand long to face break point. She responded with a biting serve into the body. Attacking net, Williams in prime position to put away a backhand volley but banged a swing volley into the net to face a second break point.

Playing exclusively to Venus' forehand, Jankovic paid the price for predictable play when Williams lashed a forehand winner up the line. Hitting off her back foot, Jankovic lined an inside out forehand into the net.

Attacking behind another flat forehand down the line, Williams was tested by a Jankovic running lob and her high backhand volley missed the mark wide. It was deuce. Williams angled a short backhand volley then knocked off a challenging high backhand volley to earn game point.

She ended an arduous game, holding for 4-3, when Jankovic sprayed a backhand crosscourt wide.

Pounding away at Williams' forehand, Jankovic held at 15 when the defending champion put a running forehand into the net, to forge a 4-all tie.

In the 10th game, Williams pounded down an easy overhead for 0-15 then fired a forehand winner down the line for 0-30. She was two points from the opening set, but Jankovic made sure she did not get any closer. On the strength of three straight first serves, Jankovic reeled off four consecutive points for 5-all.

the momentum shifted dramatically as Williams played her way out of the set, banging a backhand into net then sailing a forehand beyond the baseline to face triple break point. She buried a serve into the body to fend off  the first break point, smacked a strong forehand winner down the line to save the second break point. Patiently picking at the forehand side, Jankovic drew a wild forehand error that nearly missed the doubles alley to break for 6-5.

Serving for the set, Jankovic reached double set point when Williams' forehand return floated beyond the baseline. Defending with determination and depth, Jankovic drew yet another forehand error from Williams to take the opening set in 59 minutes.

Venus played more explosive — and erratic — tennis, committing 23 unforced errors compared to 10 for Jankovic, who was content to play consistent counter-punching tennis and wait for Williams to miss.