NEW YORK » Venus Williams arrived at this U.S. Open with a bum knee. She hadn’t played a match in more than two months. She hadn’t reached the semifinals at any Grand Slam tournament in more than a year.

And now? Williams is two victories away from her first U.S. Open title since 2001.

The No. 3-seeded Williams overcame nine double-faults and a total of 33 unforced errors to beat reigning French Open champion Francesca Schiavone 7-6 (5), 6-4 in the quarterfinals last night.

"I want to be in the final, because then obviously it’s just one more step," the 30-year-old Williams said. "But I’m just focused on the semis, and I don’t get too excited unless the tournament is over."

Next up for Williams is a semifinal against defending champion Kim Clijsters, who ran her U.S. Open winning streak to 19 matches by eliminating French Open runner-up Sam Stosur 6-4, 5-7, 6-3. Clijsters and Williams have split their 12 previous meetings, but the Belgian won the most recent four, including in the fourth round in New York in 2009.

"Venus is a great competitor. She’s been playing some really great tennis these last few matches," Clijsters said. "I look forward to it. It’s a challenge."

Williams is the only American singles player left in the 2010 tournament, because the last of the country’s 15 men in the field, 20th-seeded Sam Querrey, lost 7-6 (9), 6-7 (5), 7-5, 4-6, 6-4 to No. 25 Stanislas Wawrinka of Switzerland earlier yesterday.

Rafael Nadal won his 18th consecutive Grand Slam match by beating fellow Spaniard Feliciano Lopez 6-3, 6-4, 6-4.

Wawrinka, who joins Roger Federer to give Switzerland two quarterfinalists at a major for the first time, takes on No. 12 Mikhail Youzhny of Russia for a semifinal berth. Youzhny eliminated unseeded Tommy Robredo of Spain 7-5, 6-2, 4-6, 6-4.