Federer has won 39 consecutive matches at the American Grand Slam tournament, where he is trying to become the first man since Bill Tilden in the 1920s to win six titles in a row.

In Saturday's semifinals, Federer will play No. 4 Novak Djokovic, who eliminated No. 10 Fernando Verdasco of Spain 7-6 (2), 1-6, 7-5, 6-2 earlier Wednesday.

Federer beat Djokovic in the 2007 final and 2008 semifinals at Flushing Meadows.

A trainer treated 10th-ranked Verdasco for a stomach muscle problem during their quarterfinal in Arthur Ashe Stadium.

There were no such problems for teenager Yanina Wickmayer, who advanced to her first Grand Slam semifinal 10 years after she and her father left behind their lives in Belgium to chase her tennis dream in America.

The unseeded Wickmayer beat Kateryna Bondarenko 7-5, 6-4 to joins fellow Belgian Kim Clijsters in the semis, where she will face another 19-year-old _ ninth-seeded Caroline Wozniacki, the first Dane to reach the singles semifinals at a Grand Slam. Wozniacki routed 17-year-old American Melanie Oudin 6-2, 6-2.

Clijsters, the 2005 champion on the comeback after two years on the sidelines, will play defending champion Serena Williams in the other women's semifinal.

Wozniacki, who until now was the highest ranked player on tour yet to reach a major semifinal, won 14 of the first 18 points under the bright lights and kept on cruising against crowd favorite Oudin. She won the last five games of the match, ignoring a partisan crowd that cheered when she double-faulted.

Ranked 50th, Wickmayer had never made it past the second round at a Grand Slam. But her journey to this point has inspiring.

When she was 9, her mother died of cancer, and little Yanina set out to find a fresh start, researching tennis academies on the Internet before settling on one in Florida.

Talk about precocious, ambitious and adventurous: Yanina had only recently started playing tennis. Neither she nor her father spoke English.

But this is what had to be done.

Her father closed his pool construction company in Belgium, and relatives supported the pair financially while they lived in Florida for 2 1/2 years.

"He just gave everything up for me," Yanina said. "He just left. He listened to a girl that was 9 years old and left his life, left his dreams. I'm always going to respect him for that."

Marc Wickmayer was in the Arthur Ashe Stadium stands Wednesday, watching his daughter play the biggest match of her career _ and win it.

"I have no words for what he's done," Yanina said. "There is no way of thanking him in any way for what he did, but I hope with my semis here this week, I can show him that I really thank him for everything."