Kerri Walsh and Misty May-Treanor are closer to their third consecutive gold medal after a dramatic victory over China in the semifinal 22-20, 22-20.
It was the 20th straight Olympic victory for May-Treanor and Walsh, and they had never lost an Olympic set before last week, when they beat Austria 2-1 in pool play.
Walsh and May-Treanor will play the other American team, Jennifer Kessy and April Ross, who beat Brazilians Larissa Franca and Juliana Silva in the late semifinal 15-21, 21-19, 15-12.
The final is Wednesday night.
Aly Raisman, captain of the U.S. women's gymnastics team, finished the Olympics with a gold medal on floor exercise.
Raisman becomes to first American woman to win in that event, and matched Gabby Douglas in gold medals. With her bronze on balance beam earlier in the day, she is now the most decorated of the Fierce Five.
Energized by her surprise bronze on beam, Raisman's floor routine had an extra spark. Her tumbling passes were some of the most difficult, and she got such great height on them you could have parked a double-decker bus beneath her. Her landings were not only secure, one was so powerful it practically shook the floor.
The rest of the Americans came up empty-handed, with Douglas having another rough day. She finished seventh on balance beam after a fall.
"I'm so happy, going home with two Olympic gold medals and a couple of titles under my belt," Douglas said. "I'm so happy for Aly, she deserves to be up on that podium."
World champion Jordyn Wieber, voted most likely to leave the Olympics with the biggest haul, was seventh on floor and finished without any individual medals.
In men's gymnastics, Danell Leyva and Jonathan Horton were fifth and sixth, respectively, on high bar, leaving the U.S. men with only Leyva's all-around bronze.
On the track, Usain Bolt breezed into the 200-meter semifinals, while on the basketball court, 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 Associated Press contributed to this report.