Medal chances for the U.S. team in the women's competition were precarious after Argentina beat the United States, 2-1.
The U.S. team protested, taking their case to the seven-person Jury of Appeals about an hour after the game, claiming they lost critical seconds when an Argentine player was hurt late in the game.
A decision on the appeal was delayed until today.
The U.S. team had a penalty corner with two seconds left, and the clock stopped because of an injury. The U.S. side believed more time should have been left on the clock before Barb Marois' final shot went wide.
In other women's games, defending Olympic champion Spain tied Great Britain, 2-2; Germany lost, 4-3, to the Netherlands; and Australia tied South Korea, 3-3.
In men's competition, the Netherlands stayed unbeaten with a 3-2 victory over Australia.
South Africa came back from a two-goal deficit to gain a 3-3 tie with South Korea, and Britain and Malaysia tied, 2-2.