Williams, who is competing in singles and with her sister Venus in women's doubles, had repeatedly said she also wanted to play mixed doubles. Andy Roddick, Bob Bryan and John Isner all sought her as a partner.
"I really wanted to play with Andy and Bob, and I couldn't decide," Williams said. "I can't choose."
In addition, Williams said, she concluded three events were too many. Instead she deferred to Huber, who shares the No. 1 ranking in women's doubles with Raymond.
"I don't think it would be appropriate for me to play all three," Williams said. "I thought, Liezel is such a great teammate and team player — why shouldn't she be able to play two events and win the gold for the USA?"
Huber and her mixed doubles partner, Bob Bryan, have won two Grand Slam titles together. The other U.S. team will be Raymond and Mike Bryan, who won their third major title together at Wimbledon this summer.
Other entries for the competition beginning Wednesday include Lleyton Hewitt and Samantha Stosur of Australia, Victoria Azarenka and Max Mirnyi of Belarus, and Juan Martin del Potro and Gisela Dulko of Argentina.
Teams were entered Tuesday by each nation's Olympic committee. U.S. coach Mary Joe Fernandez said she was happy with her team's entries, adding that three events might have stretched Serena Williams too thin.
"It's a lot of matches in a short amount of time," Fernandez said. "You don't want to jeopardize the other events. We're lucky we have so many possibilities in matchups."
Venus Williams wasn't expected to play mixed doubles because she's already in two other events and dealing with an autoimmune disease that causes fatigue.
She said she and Serena will be glad to concentrate on singles and their doubles partnership.
"We already have a ton of matches ahead of us in just a few days, so I think it was better for us to focus on these two events," Venus said.
Mixed doubles is in the Olympics for the first time since 1924. Competition involves 16 teams, meaning only two victories are needed to reach the medal round.
While the U.S. entries lack the anticipated star power, they'll be formidable. The Bryan twins are competing as a team in men's doubles and seeded No. 1. The Huber-Raymond partnership is seeded No. 1 in women's doubles.
"What's most important is bringing home medals for the U.S.," Venus Williams said.