Game 21 of the World Chess Championship in Lyon, France, was postponed yesterday at the request of defending champion Gary Kasparov. The game has been rescheduled for tomorrow, with challenger Anatoly Karpov playing white.

Kasparov, who won Game 20 on Saturday, leads Karpov by an overwhelming score of 11 to 9, with a maximum of four games remaining in the match. He will take a first prize of $1.7 million if he reaches 12 1/2 points; if he reaches only 12 points, he still keeps his title but splits the $3 million prize. A draw is worth one-half point for each player, while a win earns a point. In order for Karpov to recapture the title he lost to Kasparov in 1985, he would have to win at least three of the four games remaining.

Kasparov has now used his three timeouts, while Karpov still has one left. This is not the first time Kasparov has taken a timeout after a victory, though timeouts are more often taken to recover from a defeat. According to one theory, Kasparov's optimism after a victory has sometimes led him to take unnecessary risks, so this timeout may be a way of cooling off.