The U.S. women's volleyball team remained undefeated at the London Games with a straight-set victory over the Dominican Republic on Tuesday night to advance to the semifinals.

The United States easily managed the 25-14, 25-21, 25-22 sweep without captain Lindsey Berg, who hurt her left ankle in the team's final preliminary round match against Turkey on Sunday. Courtney Thompson started in her place as setter.

The top-ranked U.S. team, with six straight victories, will play the winner of Tuesday's late match between Italy and South Korea. The other semifinal Thursday was set when both Japan and Brazil won their quarterfinal matches earlier in the day.

Destinee Hooker scored 19 points for the United States, which has never won a gold medal in indoor volleyball. The team fell just short at the Beijing Games, taking home the silver after falling in the final to Brazil.

Now, playing under Hugh McCutcheon, who led the U.S. men to the gold in Beijing, the United States is among the favorites in the tournament.

The Americans took over top spot in the world rankings at the end of 2011, ending Brazil's four-year run at No. 1. The women qualified for the Olympics in November with a silver-medal finish in the FIVB World Cup.

The U.S. beat No. 2 Brazil 3-1 in a preliminary-round rematch of the Beijing final last week.

The 11th-ranked Dominican Republic finished 2-3 in pool play, beating both Algeria and Britain in straight sets. The Dominicans' only other Olympic appearance was at the Athens Games, where they upset the United States 3-2 but finished in 11th.

The Americans have defeated the Dominican Republic three times this year, most recently in a four-set semifinal match at the Pan American Cup.

The United States jumped out to a 12-3 lead and rolled through the first set, winning it on Foluke Akinradewo's block.

While clearly overmatched, the Dominican Republic took an 8-6 lead in the second set on Candida Estafany Arias Perez. The United States regained the lead when Hooker's spike made it 11-10.

The Dominicans denied the U.S. set point three times, but Jordan Larson eventually spiked to win it.

The U.S. took an 18-12 lead on Christa Harmotto's spike, but the Dominicans closed to within 19-18 before the Americans won it on Bethania de la Cruz de Pena's misplayed kill.

Prisilla Altagracia Rivera Brens finished with 15 points for the Dominican Republic.

It was unclear if the U.S. team held out Berg -- a three-time Olympian -- to give her extra rest before the semifinals, or if she was unable to play because of the ankle injury. She dressed and warmed up with the team Tuesday's quarterfinal with no visible limp.

Thompson, a 27-year-old first-time Olympian, helped the Americans to a bronze medal at the 2011 Pan American Games, including the four-set win over the Dominicans.

Often during timeouts Berg would pull Thompson aside to confer.

Earlier Tuesday, defending champion Brazil denied Russia match point six times before winning 3-2 to earn a spot in the semifinals.

The Brazilians will face Japan, which used finesse to counter strength in a 3-2 victory over China.