LYON, FRANCE, DEC. 5 -- Anatoly Karpov put new excitement in the World Chess Championship match today by relentlessly pushing titleholder Gary Kasparov into a defensive crouch and winning the 17th game of their series.

The two are now tied at 8 1/2 points apiece, with seven games left to play.

Karpov tied the score in a 40-move game played in one sitting. It was in sharp contrast to Tuesday, when he lost in one of the longest championship chess games ever played -- one of 102 moves that lasted more than 12 hours and was spread over three days.

Karpov, playing white, showed no signs of fatigue as play began today. At the outset, former champion Boris Spassky, chief commentator at the match, said Karpov had "great chances" of coming from behind to win the 24-game match. Kasparov, Spassky said, "has no more energy to play."

Only a day earlier, observers said both players appeared exhausted.

Today's game was played to a standing-room-only crowd in a hall in Lyon, France, that seats more than 900 people. Included as observers were a number of newly arrived grandmasters fresh from a chess olympiad in Novi Sad, Yugoslavia.

Karpov opened with pawn to Queen 4, and Kasparov defended, as he has before, with the Grunfeld-Indian defense. The moves were a repeat of earlier performances until black varied with 9 ... Bg4. Karpov's reaction was a surprising 10. Ng5, ready to meet 10 ... h6 with 11. h3, a complicated position that would work in white's favor.

After 18 moves, the pieces were in a typical Grunfeld position, with both players having equal chances to win. Kasparov, however, dissatisfied with the position of a knight on a5, moved it to c4, setting up an exchange that gave Karpov command of the game through control of the c file with a rook.

Kasparov then set out to trade rooks. But white parried with 26. Rc6, a move that sealed the game. Earlier in the tournament, Hungarian grandmaster Lajos Portisch, an adviser to Karpov, had kept a stony silence while play was going on. Today he offered commentary to reporters frequently as the game progressed, and said the champion had blundered by overlooking that decisive move.

Black at that point was forced to choose between two evils -- either conceding the c line to Karpov's heavy pieces or exchanging the rooks and giving white a very strong passed pawn.

Kasparov chose to keep the rooks on the board, but Karpov, playing precisely, got his passed pawn anyway, and pushed it to the seventh rank on move 38. Kasparov, totally stifled, resigned two moves later.

At stake should either player reach 12 1/2 points is $1.7 million of a $3 million kitty. If the two end in a 12-12 tie, they will split the money evenly, with Kasparov retaining the title. To date, each has won two games, and there have been 13 draws. Game 18 is scheduled for Saturday.

With the end of the Novi Sad olympiad, more grandmasters will be arriving in Lyon. The Soviet Union won that competition; the team from the United States surprised many by finishing second, placing ahead of a strong Britishteam in a tiebreaker.

Kavalek is an international grandmaster and was in Lyon for Game 17. Sussman is a Washington writer and opinion analyst.

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