US OPEN
Venue: Flushing Meadows, New York Date: 31 August - 13 September
BBC coverage: Live text commentaries on the website from 1600 BST each day, regular updates on 5 live, full commentary on 5 live sports extra in week two, both finals on 5 live
**World number two Serena Williams was forced to dig deep as she reached the US Open fourth round with a 6-3 7-5 win over Maria Jose Martinez Sanchez.**The American, who accused Martinez-Sanchez of cheating when they met at the French Open this year, was in brutal form as she snatched the opener.
But the Spaniard fought hard in the second, before being broken late on.
Williams will now go on to face Slovak Daniela Hantuchova, who beat American Vania King 6-2 6-3 earlier in the day.
The number 22 seed was never in trouble as she struck 25 winners on her way to four breaks of serve, with King unable to live with **Hantuchova’s **guile and speed across the court.
Italy’s Flavia Pennetta was the first woman into the fourth-round draw as she underlined her US Open challenge with another rapid-fire win.
“Tennis, it’s a very strange sport”
Flavia Pennetta
The 27-year-old 10th seed demolished Canada’s Aleksandra Wozniak 6-1 6-1, meaning she has lost only four games in three rounds.
Pennetta, making her sixth appearance at the US Open, has made giant strides forward this year, building on an excellent 2008 when she reached the last eight here and the fourth round at the French Open.
And she said: “Tennis, it’s a very strange sport, because for one point everything can change. You have to be very mentally focused at all moments.”
Pennetta’s compatriot Francesca Schiavone, seeded 26th, also progressed, securing a hard-fought victory over Belarussian eighth seed Victoria Azarenka.
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Azarenka looked on course for an expected win when she took the first set, but was undone by a total of 30 winners from Schiavone as the Italian won through 4-6 6-2 6-2.
Serena’s sister Venus, the third seed, is first up in the night session against Magdalena Rybarikova of Slovakia, while former champion Kim Clijsters of Belgium will continue her comeback after a two-year break against compatriot Kirsten Flipkens.