NEW YORK, April 17: Venus Williams advanced to her first semifinal of the year with a 6-3 6-4 victory over Vera Zvonareva at the Family Circle Cup in Charleston, South Carolina on Friday.

The American is the fourth seed at this event and with the top three players all withdrawing, was a huge fan favourite against the ninth-seeded Russian.

The partisan support had a lot to be happy about as did Williams, who won four straight games in the second set to close out the match.

In other quarterfinal action, 11th seed Patty Schnyder caused the biggest upset of the round when the Swiss left-hander defeated fifth-seeded American Lindsay Davenport 6-3 6-2.

Schnyder needed just 52 minutes to end Davenport's good run of form that stretched back to the Californian's win at Amelia Island last week.

Davenport lost the first four games of the first set and never seemed to recover.

In the semifinals, Williams plays Croatia's Jelena Kostanic, who defeated Hungary's Petra Mandula 7-6 6-2 to stay on course for her first tour victory.

Schnyder meets 16th-seeded Conchita Martinez of Spain in Saturday's other semifinal.

Martinez celebrated her 32nd birthday in style, easing past eighth-seeded Nadia Petrova of Russia 6-3 6-1.

WTA results

Patty Schnyder (Switzerland) bt Lindsay Davenport (U.S.) 6-3 6-2; Jelena Kostanic (Croatia) bt Petra Mandula (Hungary) 7-6 (7-4) 6-2; Venus Williams (U.S.) bt Vera Zvonareva (Russia) 6-3 6-4; Conchita Martinez (Spain) bt Nadia Petrova (Russia) 6-3 6-1

Roddick struggles

HOUSTON (Texas): Top seed Andy Roddick fought off a stiff challenge from Austrian Jurgen Melzer on Friday night to reach the semifinals of the US Men's Clay Court Championships.

Seeking a fourth straight appearance in the final here, Roddick advanced with a 7-5, 7-6 (7/5) victory to improve his match record in this tournament to 17-1.

The 21-year-old American won back-to-back titles in 2001-02 and was runner-up to Andre Agassi a year ago. He has won an ATP Tour-best 31 matches this season.

Roddick has won 11 straight matches, dating to his victory at the Tennis Masters Series event in Miami, where he captured his third ATP Masters Series title.

Roddick was down a break midway through the opening set but broke back and then again to take the first set. The two held serve throughout the second with Roddick threatening to break at both 4-3 and 6-5 before winning in a tiebreak.

Germany's Tommy Haas locked up another semi-final berth, continuing his comeback with a 6-2, 6-0 drubbing of Russian Dmitry Tursunov. After missing all of last season with a shoulder injury, Haas reached his first semi-final since August 2002 at Long Island.

Fifth seed Andrei Pavel of Romania ousted fourth-seeded American James Blake 6-4, 6-4 to line up a semifinal clash with Haas.

Pavel earned a clutch break at three-all in the first set after a long game with several deuce points to take the first set. He was up 5-2 in the second when Blake broke him and held to get back to 5-4. But Pavel held off the American with an ace on match point.

Seventh-seeded Luis Horna of Peru earned a shot at Roddick with a 7-5, 6-3 victory over US veteran Todd Martin.

Results Andy Roddick (U.S.) bt Jurgen Melzer (Austria) 7-5 7-6 (7-5); Luis Horna (Peru) bt Todd Martin (U.S.) 7-5 6-3; Andrei Pavel (Romania) bt James Blake (U.S.) 6-4 6-4; Tommy Haas (Germany) bt Dmitry Tursunov (Russia) 6-2 6-0

Estoril Open results

ESTORIL (Portugal): Results on the sixth day of the 748,850-euro Estoril Open on Saturday:

Men semifinals: Juan Chela (ARG) bt Florian Mayer (GER) 6-3, 6-3; Marat Safin (RUS bt Iralki Labadze (GEO) 2-3 - retired

Women semifinals: Emilie Loit (FRA) bt Marta Marrero (SPA) 6-4, 6-4; Iveta Benesova (CZE) bt Stephanie Cohen-Aloro (FRA) 6-3, 7-5.-Agencies