China leads the United States by one medal going into the second week of the Olympics in London.
Track and field contests will be among the highlights this week. Usain Bolt proved himself to be the fastest man in the world on Sunday. The Jamaican sprinter successfully defended his gold medal in the 100-meter dash. American Justin Gatlin won the bronze.
In tennis, Serena and Venus Williams won the gold in women's doubles. Their victory came right after Serena won the gold in women's singles.
"It's incredible," Venus said. "Coming off Serena's victory, I think most of all we are happy to add to our country's medal count and be a part of it.
"We're definitely planning on Rio," she added. "We're going out with a bang in Rio. Hopefully we will make it four, you never know."
In gymnastics, a rare mistake cost American McKayla Maroney the gold medal on the vault. But she said she's still happy with the silver.
''It happens. It's gymnastics,'' Maroney said. ''You can't be perfect, and sometimes things don't go as you planned.''