The battle of the yogurt escalated over the weekend at the world championship chess match in the Philippines. Attempting to find a common ground on the issue of food at the chess table during the five-hour games, the International Chess Federation received an ultimatum from champion Anatoly Karpov's camp: The champion will eat only fresh, not frozen food, and he will not eat any food (even yogurt) that is not prepared by members of his entourage.

Challenger Victor Korchnoi prepares for each game by eating a can of caviar (Iranian, not Russian) and brings snacks to the table with him before the game. He suggested that Karpov could do likewise.

After pondering Korchnoi's complaint that a cup of yogurt delivered to Karpov during a game might have a secret code meaning, the International Chess Federation suggested that each player could have a refrigerator and a hot plate in his dressing room and that they could order food from a restaurant during a game. Neither suggestion was found acceptable by the Soviet delegation which will not allow any non-Russian to prepare food for the champion and will not accept frozen food.

The Russians said they would have a counter-proposal before the fourth game of the match, which is scheduled to begin today.

The tempest in a yogurt cup began when Korchnoi's seconds formally protested the delivery of a cup of blueberry yogurt to Karpov at the 24th move of the second game in each match. Delivery of the yogurt might mean "offer a draw immediately," the protest suggested - and, in fact, Karpov did offer a draw a few moves later. The protest "was a joke. I think," said chief referee Lothar Schmid, but the Russians are taking it seriously.