The triumph also lifted the 26-year-old back to the summit of the world rankings for the first time since August 2003 and this time she does not want to let go.
Top seed Nicole Vaidisova was dumped out of the Family Circle Cup on Tuesday in a second-round loss to Michaella Krajicek.
World No 1 Serena Williams's 27-match unbeaten run ended with a 6-2, 6-3 defeat by Petra Kvitova in the Madrid Open.
If humility was a sign of a true champion then unseeded Czech Petra Kvitova would be in with a real chance of upsetting the odds and beating Serena Williams in their semi-final showdown on Thursday.
Former champion Serena Williams shocked the French Open crowd, and herself, by losing to Virginie Razzano in the first round on Tuesday, her earliest exit from a grand slam in the 47 appearances she has made in an outstanding career.
Serena Williams may be the overwhelming favorite but the World No 1 is anything but a sure bet to win a U.S. Open overflowing with intriguing possibilities.
Clijsters says she hopes she has discovered the "magic formula" to beating the Williams sisters.
Defending champion Serena Williams was knocked out by Jelena Jankovic in the quarter-finals of the Australian Open.
Serena Williams was left all alone trying to crush an unlikely uprising on Wimbledon's hallowed lawns on Tuesday as sister Venus and Kim Clijsters suffered shock defeats in the women's quarter-finals.
Petra Kvitova's hopes of defending her Wimbledon title were shot to pieces in a hail of Centre Court cannon fire from Serena Williams who ousted the defending champion 6-3, 7-5 in their quarter-final on Tuesday.
Serena Williams admitted that a bad back sustained during practice hampered her movement during her shock fourth round loss to Ana Ivanovic on Sunday, but refused to blame the injury for her stunning exit that blew the Australian Open wide open.
Serena's coach said it had been a winding road following the birth of her daughter in 2017 to the kind of peak performance that brought her US Open success in the past.
The American hit back at claims that she exaggerated her calf injury during her dramatic fourth round victory over Daniela Hantuchova.
"The official diagnosis by the doctor was that he was shocked that I was playing this many tournaments in the beginning," Williams said.
IMAGES from the Australian Open matches played on Friday.
