Fourth seeded American Serena Williams routed Dane Caroline Wozniacki 6-0, 6-3 in the quarter-final match of 2012 London Olympics being played at All England Club, Wimbledon.

"It wasn't a quick first set - it was 32 minutes, it's not as if it was 15 minutes," said Serena. "She was playing really tough. But I know I can rally up to a hundred balls if necessary, and when you're playing Caroline you have to be ready to do that. She's so consistent - she was No.1 for a reason."

"No matter what happened, I'm in a medal round now so I'm very excited."

The American next faces Belarussian and top seeded Victoria Azarenka, who edged past seventh seeded Angelique Kerber 6-4, 7-5.

"We had the longest rallies. At one point I just couldn't believe when it was going to be over during the point," Azarenka said. "It was a really tough one, a very good match from both of us. We showed very high quality tennis and a big fight today, and there's nothing more that you could ask from both of us.

"It was important to take command first and stay aggressive. It was very difficult to do it all the time against her, but in the end I think I got it the most."