Second-seeded Roger Federer of Switzerland advanced to his 38th Grand Slam semifinal with a win in straight sets over 12th-seeded Richard Gasquet of France on Wednesday evening in a U.S. Open men's quarterfinal in New York.
Wawrinka, the fifth seed, rolled to a 6-4, 6-4, 6-0 victory over South African Kevin Anderson, the No. 15 seed. Anderson had ousted third-seeded Andy Murray to reach his first career Grand Slam quarterfinal, but he had 42 unforced errors against Wawrinka.
In women's play, second-seeded Simona Halep of Romania advanced to her third career Grand Slam semifinal, beating 20th-seeded Victoria Azarenka of Belarus 6-3, 4-6, 6-4 in the quarterfinals.
The match was delayed early in the third set by rain.
The other women's semifinal will feature top-seeded Serena Williams against unseeded Italian Roberta Vinci. The other men's semifinal later this week will feature top-seeded Novak Djokovic of Serbia and ninth-seeded Marin Cilic of Croatia, the defending champion.
Halep reached the 2014 French Open final and the semifinals at Wimbledon last year.
Pennetta, 33, is headed to her second semifinal in a major event, with the other being the 2013 U.S. Open. She prevailed Wednesday afternoon despite extreme heat and humidity.
"It's not just the heat, it's the tension of the match, and what you're thinking," Pennetta said. "There are so many things in your mind. You have to take everything and just play your tennis. It's not a good feeling when you feel so tired and you can't move very well. We played a really tough match for more than two hours."