Dax Holdren and Stein Metzger dodged "the Recking Ball" and advanced to the beach volleyball quarterfinals.
Delivering their best performance of the tournament, the 12th-seeded U.S. duo upset fourth-seeded Germans Markus Dieckmann and Jonas Reckermann, 21-16, 19-21, 15-13, in their first match of the medal round.
The 6-foot-6 Reckermann, a spiking specialist colorfully nicknamed by Holdren, was reduced to a harmless setter most of the match as the Americans focused on serving to the 6-2 Dieckmann.
"The only way to beat that team is to keep Reckermann out of the play," Metzger said. "Our strategy was, 'Give it to the little guy.' "
The Americans embraced after the match, falling backward into the sand. They kept alive the possibility of a third straight American gold at the beach. Karch Kiraly and Kent Steffes won the first in 1996, when the sport made its Olympic debut. Dain Blanton and Eric Fonoimoana made a surprising run to the gold in Sydney.
The Americans will now face fifth-seeded Swiss pair Stefan Kobel and Patrick Heuscher, who ousted Joao Brehna and Luis Maia of Portugal, 21-18, 21-19.
"It's an uphill battle," Metzger said. "We need to keep getting better and better if we want to win this."
Park Sung Hyun shot a 10 on the last arrow of the women's team competition at Panathinaiko Stadium, giving South Korea a 241-240 win over China and its fifth consecutive gold medal in the event.
Taiwan defeated France, 242-228, to win the bronze.
Kim Dong Moon and Ha Tae Kwon of South Korea won the gold medal in men's doubles, beating compatriots Lee Dong Soo and Yoo Yong Sung. Indonesia's Eng Hian and Flandy Limpele won the bronze medal.
Claudio Liverziani hit a two-run homer in the top of the ninth inning to put the Italians ahead, and they held on for a 5-4 win over Taiwan, their first of the tournament. Peter Nyari pitched 22/3 innings of scoreless relief to earn the win.
Chris Hoy of Britain won the gold medal in the one-kilometer time trial with an Olympic record of 1 minute 0.711 seconds. Arnaud Tournant of France won silver at 1:00.896 seconds and Stefan Nimke of Germany took the bronze at 1:01.186.
Anna Meares of Australia won gold in the women's 500-meter time trial, establishing a world record of 33.952 seconds. Jiang Yonghua of China, whose mark was broken, won the silver in 34.112. Natallia Tsylinskaya of Belarus took bronze in 34.167.
Laura Wilkinson saved her best for last, and the defending Olympic gold medalist advanced past the preliminaries of the 10-meter platform.
The 26-year-old Texan came through on her final dive, a backward 21/2 somersault with 11/2 twists. Her spins were crisp and her entry smooth, resulting in scores of 7.5 and 8.0 across the board. That was enough to move her to 13th with 314.19 points.
Germany opened a sizable lead in grand prix dressage team competition, leading with a team average of 71.813 percent. The Americans were second with 69.146 percent and Britain was third with 69.084 percent.
The remaining two riders for each team ride today to determine team medals, with the top three scores counting.
Russia used a patient, defensive strategy to defeat Germany, 34-28, and win the gold medal in women's team epee.
Canada fell to France, 45-37, in the bronze medal bout.
Challenged for the first time in these Olympics, the U.S. women's team fought through foul problems and long stretches of cold shooting to clinch first place in its preliminary group with a 71-58 victory over Spain.
The United States had won its first three games in Athens by an average of 31 points, but nothing came easily against Spain. Lisa Leslie, Tina Thompson and Yolanda Griffith led a 10-2 fourth-quarter run that put the Americans firmly in control.
Leslie led the United States with 19 points, 15 in the first half.
Yukiko Ueno pitched the first perfect game in Olympic history, leading Japan to a 2-0 win over China and a spot in the semifinals.
The 22-year-old Ueno overpowered the Chinese in a game the defending silver medalists had to win. A loss would have dropped Japan (4-3) into a tie with Canada, which would have won the tiebreaker and the No. 4 spot in the semis because it beat Japan in Tuesday's preliminary round.
Keiji Suzuki, in the men's 100+kg category, and Maki Tsukada, in women's 78+kg, won gold medals to give Japan the Olympic title in eight of 14 events -- a record haul for the country that invented the sport.
China's team of Wang Nan and Zhang Yining won the gold medal in women's doubles, beating Lee Eun Sil and Suk Eun Mi of South Korea, 11-9, 11-7, 11-6, 11-6.
Guo Yue and Niu Jianfeng of China won the bronze.
Unseeded American Mardy Fish beat No. 16 Fernando Gonzalez of Chile, 3-6, 6-3, 6-4, in the semifinals.
In tomorrow's final, Fish will play No. 10 Nicolas Massu, who defeated Taylor Dent, 7-6 (7-5), 6-1, in another U.S.-Chile match.
In the women's doubles semifinals, No. 8 Li Ting and Sun Tian Tian of China beat No. 7 Paola Suarez and Patricia Tarabini of Argentina, 6-2, 2-6, 9-7, guaranteeing China its first tennis medal at an Olympics.
Li and Sun will face No. 2 Conchita Martinez and Virginia Ruano Pascual of Spain for the gold tomorrow. The Spaniards were 6-3, 6-0 winners over No. 5 Shinobu Asagoe and Ai Sugiyama of Japan.
Anna Dogonadze of Germany won the gold medal, scoring 39.60 points of a possible 40 to edge Karen Cockburn of Canada. Huang Shanshan of China took bronze with 39.00.