The Chinese girls, who claimed the gold medal in an epic final against Russia in the Athens Games four years ago, edged out the same opponents 25-22, 27-25, 25-19 in the one hour and 24 minutes thriller.

In an earlier quarterfinal, world number one team Brazil was hardly tested before blitzing Japan 25-12, 25-20, 25-16 in just 67 minutes.

The team, labeled as the heaviest favorite for the gold medal, has now compiled a 6-0 clean sheet since the preliminaries and did not even drop one single set.

"It will be a very difficult match against Russia or China but our team is confident because of the way we have been playing," said Brazilian winger Sheilla Castro, the best scorer of the team.

Cuba also pulled off a solid game to beat Serbia 26-24, 25-19, 26-24, and will in the other semifinal take on the United States, who survived a five-set thriller to beat World Cup winner Italy.

The United States twice rallied from one set down to force a tie-breaker, which they won at 15-6.

"I felt very happy with the result, they can always bring me surprise. I am so proud of them," American head coach Lang Ping, a former Chinese player, said after the match.

Cuba, former world champions and Athens bronze medalists, met serious challenge from the Serbian girls in the beginning of the match. The opening set was close as either of the teams could pull away until the set was levelled at 24-all.

Cuban spiker Yumilka Ruiz hit an excellent smash and then an error from Serbia gave Cuba the first set.

It was in the second set that the Cuban girls, who won three straight Olympic gold medals in 1992, 1996 and 2000, have started to take control over the match.

After claiming the set at 25-19, Cuba took their opponents lightly in the third set while Serbia mounted a strong comeback and after two straight blocks from Maja Ognjenovic, the Serbian team overtook the lead at 22 -20.

However, Serbia was not consistent in the remaining time.

"We're pleased with this victory, and with the opportunity to fight for the medals. It was a tough match and Serbia are a tough team," said Cuba head coach Antonio Perdomo Estrella.

"Today's match was very difficult and both teams were under mental pressure. Despite the victory we didn't feel relaxed, and we must play better in the next two matches. All four teams will be feeling the same emotions."

Playing in a repeat of the Athens Games final, China and Russia both needed a win to stay on course especially after they compiled a disappointing 3-2 record in the preliminaries.

"We had chance to win the first and second sets, but we are troubled with our poor attack and the Chinese girls did a good job in blocking," Russian head coach Giovanni Caprara said.

The Russian girls did not give up even when they lost the first set and squandered two set points in the second set.

But in the third set, the team showed some signs of vulnerability when they were up 16-13. Since then, the match turned in China's favor, with the Russian attack stuffed on the net. China used a 12-3 run to take the set and the whole match.

"This was a very important game for us, we are so happy that we won because we knew that Russia is a very strong team," said China captain Feng Kun. "In the quarterfinals there are no weak teams, so we knew we must win every point, so we fought for each point and were successful in the end."

"This victory did not come easily. In the preliminary round we suffered setbacks, we lost two matches and we knew we needed to control our emotions in order to succeed."