KEY BISCAYNE, Fla. (AP) - Serena Williams came from behind in both sets Friday to beat top-ranked Martina Hingis and reach the final of the Lipton Championships, where she awaited a possible matchup with her older sister, Venus.

After losing the first four games, Williams rallied and defeated Hingis 6-4, 7-6 (7-3). The victory was the 16th in a row for Williams, who needs one more win for her third consecutive tournament title.

``I've worked really hard all my life since I was 4 years old,'' said Williams, 17. ``There comes a time you have to start winning. All my hard work is finally paying off.''

Defending champion Venus Williams, 18, was to play five-time Lipton champ Steffi Graf on Friday night. A victory by Venus would result in an all-sister women's final Sunday, the first since the Open era began in 1968.

Richard Krajicek will try for his first U.S. tournament title since 1993 when he plays unseeded Frenchman Sebastien Grosjean on Saturday.

Hingis, 2-0 previously against Williams, was simply overpowered this time. The difference was often startling - the final serve from Williams, for example, clocked at 110 mph, while Hingis' final serve was 84 mph. Hingis' serve is the weakest part of her game, and the muscular Williams took advantage by repeatedly ripping return winners.

But Williams was also erratic. She made nine backhand errors in one game alone, an 18-point marathon. The margin was lopsided in her column for both unforced errors (49-14) and winners (48-11).

Williams lost 13 consecutive points in the early going, setting the tone for her streaky performance.

``I was like, `OK, when do you start playing?''' Hingis said. ``She was just too confident. She thought I would miss everything.''

After Hingis won the first four games, Williams won the next eight. Hingis then won five in a row for a 5-2 lead in the second set before Williams began her final charge.

She broke Hingis' serve to reach 6-6, hit three consecutive forehand winners in the tiebreaker and slammed yet another to close out the match. Williams then broke into a grin, raised both hands and staggered across the court, as if overwhelmed by her achievement.

``I guess it's my biggest win,'' she said. ``I've never beaten the No. 1 player before, now that you mention it.''

``She played a great match,'' Hingis said. ``It's a good time for her, not for me.''

Despite the defeat, Hingis will remain No. 1 when the new rankings are released next week. Second-ranked Lindsay Davenport withdrew from the tournament with a sprained wrist after reaching the quarterfinals.