Game 23 of the world chess championship was adjourned after 40 moves last night in Seville, Spain, with challenger Anatoly Karpov struggling to stay alive. With a team of experts to help him in overnight analysis, it seemed likely he would be able to do so.

For this crucial game -- the last in which his opponent has the white pieces and therefore an opening advantage -- champion Gary Kasparov drastically revised the match strategy he has followed in recent games, changing the pace and managing to throw his opponent off balance. Kasparov is considered essentially an attacking player -- but, particularly since losing Game 16, he has taken basically passive postures, in effect insisting that Karpov must take the risks involved in trying to win. But for Game 23, with the score tied at 11-11, he apparently decided that a good offense is the best defense, and the situation at adjournment seemed to support his view.

It was Karpov who sealed his 41st move in a position where Kasparov had a strong initiative, control of the crucial, open f-file and all his pieces beautifully lined up and coordinated for an attack. If it had been Kasparov's move, rather than Karpov's, in the adjourned position, the champion could have won with 41. ... Qh4, threatening 42. ... R8f3. Karpov would have to take the black rook with his queen, and after 43. Qxf3ch, Rxf3; 44. gxf3, Qxh3ch; 45. Kg1, d3 dis. ch, black has an immediate win.

Fortunately for Karpov, it was his move. Still, the challenger faced a serious problem at adjournment; he must find a very active sealed move to disrupt the champion's initiative.

If Karpov is able to survive the immediate attack, the game will focus on the passed pawns in the center. If the game goes into an endgame, the edge will belong to the player who can unblock his center pawns and advance them. If the game becomes simplified enough, Karpov will have a theoretical edge because his passed pawns are connected.

Although he had black, Kasparov showed initiative and imagination from the beginning. First, he was able to frustrate Karpov's obvious desire to avoid the Gru nfeld Defense, cleverly transposing from an English opening into his favorite defense. There was one difference, however: In previous games, Karpov had placed his central pawns on the fourth rank; in this game, he was able to solidify with 7. e3. His plan was obviously to set up a long-range siege on the queenside, leaving the center intact. But Kasparov, returning to the kind of sharp play that comes naturally to him, began counterpunching at Move 12 and played with particular brilliance in Moves 12 to 17, essentially taking over the initiative.

The result was a complicated middle-game encounter full of tactical shots. For example if, instead of 16. e4, Karpov had played 16. dxc6, Kasparov would have won the piece back with 16. ... e4, forking two white pieces.

Kasparov's imaginative play took the wind out of Karpov's sails, and allowed the champion to dictate the tempo of the game. He was able finally to gain full control of the f-file, while Karpov could not make headway on the queenside. Kasparov's pieces simply became more active and more threatening as the game proceeded, until he reached the adjourned position.

Karpov is a genius at defense in tight positions, and he can probably find his way out of this situation. But it will take all his skill, and holding a draw will eliminate his second-last chance of winning this match.

Kasparov will have the white pieces in the 24th and last game, which is scheduled to begin tomorrow. And all he has to do to remain champion for the next three years is draw both games.

Grandmaster Lubomir Kavalek contributed to this report.