OSAKA -- Excitement ripples through the onlookers as the players take their positions on the pitch. The whistle blows, and the match begins. But just as one player clears the ball and starts racing toward the goalposts, the referee blows a whistle.

"Illegal move. The computer needs to be reset," he says.

This is one of the first of many preliminary matches at RoboCup 2005, which opened Wednesday at Osaka's Intex center. Over the next five days, teams of soccer-playing robots will advance through the preliminary rounds to the championship games, which will be held July 17.