Peszek, who was also scheduled to compete in four events, sprained her left ankle during warm-ups and only performed on the bars. Chellsie Memmel, the 2005 world all-around champion, also has been limited to bars because of an ankle injury she suffered last week.
Both teams feature specialists on each apparatus.
On the vault, Cheng will be up against Alicia Sacramone, who is a three-time world medalist in the event.
"Cheng is an amazing vaulter," said Sacramone. "We've been going head to head for the past couple of years. It will be a great competition."
Cheng is also a force to be reckoned with in the floor exercises, impressing the judges in the preliminary with her powerful and stylized performance, to the popular Chinese song "Yellow River". Her teammate, Jiang Yuyuan, also qualified for the final.
They will face Johnson, the reigning world champion, and Liukin, who finished third and fourth in preliminary.
On the beam, China will field Cheng and top qualifier Li Shanshan. Johnson, Liukin and Sacramone - second, third and fourth in the preliminary - will represent the US.
Li's performance on the beam, which had been a weak event for China, has boosted the hosts' confidence.
"We did exceptionally well on beam, which was the event we were worried about," said coach Lu Shanzhen.
Both teams are eager to improve their performances on the uneven bars, on which their top performers made huge mistakes and almost failed to reach the final.
China's Yang Yilin, the bronze medalist at the 2007 World Championships, topped the bars with a flawless routine. But Liukin promised she will come back strong.
"The Chinese have strong gymnasts, which they proved today," she said. "We've prepared really well, so all we can do is focus on our competition. We are confident we can come away with a good score."
The Chinese women are seeking to make amends for Athens, where they failed to win a single gold despite dominating the World Championships a year earlier. The US team is also eyeing the gold, which they lost to the Romanians in Athens.
"Each team has advantages and disadvantages. You can't think about what the other teams have, though. You have to concentrate on what you've got," said Bridget Sloan of the US team.
"I know a lot of people think that with the Olympics being in China, the Chinese have an advantage, but we are such a strong team right now. I guess that's team USA's advantage."
(China Daily August 12, 2008)