Diana Taurasi scored 15 points, and the U.S. women's team forced 26 turnovers in a 91-48 victory over Canada in the quarterfinals. The four-time defending gold medalists have won 39 straight games in Olympic play and will play Australia in the next round.
Australia advanced with a 75-60 victory over China. Aussie star Lauren Jackson scored 12 points to become the all-time Olympic scoring leader in women's basketball, passing former Brazilian star Janeth Arcain.
Oribe Peralta scored with a swerving long-range strike, then set up another goal with a stunning back-heel to help Mexico beat Japan 3-1 and secure a spot in the final.
Mexico will play Saturday against Brazil, which beat South Korea 3-0 in the other semifinal.
"We are guaranteed a silver, but we want a gold," Mexico coach Fernando Luis Tena said. "Mexico is a football nation. They must be partying tonight."
Brazil reached its first Olympic men's soccer final in 24 years.
The U.S. women's team played without captain Lindsey Berg but managed a 25-14, 25-21, 25-22 win over the Dominican Republic in the tournament quarterfinals.
Berg is day-to-day with a left ankle injury, and her status for Thursday's match against South Korea is uncertain.
Destinee Hooker scored 19 points for the United States, which has never won a gold in volleyball. The team took silver at the 2008 Beijing Olympics after falling in the final to Brazil.
Brazil will meet Japan in the other semifinal.
Women's water polo
Maggie Steffens scored four goals, and the U.S. women's team topped Australia 11-9 in overtime, shaking off a potentially costly blunder by coach Adam Krikorian to reach the Olympic final.
In a bruising match between medal contenders, Australia's Southern Ash converted a penalty with one second left in regulation to tie it at 9 and force overtime.
The officials awarded the penalty after Krikorian called a timeout without his team having possession of the ball.
The U.S. will meet unbeaten Spain in Thursday's final.
By the numbers
Seven of Cameroon's Olympic competitors disappeared from their official residence and may be attempting to seek asylum in Britain, the chief of the African nation's delegation said Tuesday.
The last American boxer in the men's tournament was eliminated, giving the U.S. team its first Olympic medal shutout.
Welterweight Errol Spence dropped a 16-11 decision to Russia's Andrey Zamkovoy in the quarterfinals.
Italian Josefa Idem became the first woman to compete in eight Olympic Games - and marked the occasion by upstaging a host of younger rivals to qualify for the flagship 500-meter K-1 final.
"It was a symbol to let every emotion come out of me. Now, I'm addicted to it. If you see me coming out the stadium without a shirt, you know it was good."
- German discus gold medalist Robert Harting, who ripped off his shirt, flexed his muscles and sprinted down the track after winning.