The United States, lagging 73-70 behind China in the medal count, is looking to take the lead in the remaining days of the track and field contests.

In the women's 100-meter hurdles, Americans Dawn Harper and Kellie Wells took silver and bronze respectively.

"I want to do something for my city,'' Harper told ESPN. "I want to throw a party. I want to give back. I want to say, 'You have done so, so much to appreciate me, and I want to show I appreciate you.'"

Also in track and field, American Leonel Manzano took the silver in the men's 1500 meters.

In gymnastics, U.S. team captain Aly Raisman won an individual gold in the floor exercise. She also took the bronze on the balance beam Tuesday.

But Gabby Douglas and Jordyn Wieber both came away empty-handed. Douglas fell on the balance beam, and coaches say a possible stress fracture in Wieber's leg may have kept her from doing as well in the floor exercise.

Meanwhile, the U.S. is guaranteed to win the gold and silver in women's beach volleyball. That's because both U.S. teams have advanced to the final.

Two-time Olympic champions Misty May-Treanor and Kerri Walsh-Jennings will take on Jennifer Kessy and April Ross.