Gary Kasparov took a major step toward retaining the world chess title yesterday by putting a quick finish to one of the longest games ever played in a championship series.

Resuming Game 16 after two adjournments, 88 moves and 11 hours of play over two days, Kasparov, playing white, needed only six moves to get into a position where victory was assured. Eight moves after that, the challenger, former champion Anatoly Karpov, resigned.

The victory gives Kasparov an 8 1/2 to 7 1/2 lead in the 24-game series. That seemingly slight edge is a commanding one. If the match ends in a 12-12 tie, Kasparov keeps the championship. Thus, for every game Kasparov wins from here on, Karpov must win three if the title is to change hands. Should Kasparov not win any, Karpov would still have to win two to regain the title.

Such a scenario would mean a sharp reversal of form. Of the 16 games to date, Kasparov has won two, Karpov one, and 13 have ended in draws.

When play in Lyon, France, adjourned Sunday, only eight pieces were left on the board. Aside from their kings, Kasparov had a rook, bishop and pawn and Karpov a bishop, knight and pawn. Kasparov had a clear edge in material. He also had Karpov's king stuck on the eighth rank and Karpov's knight unable to move without being taken. Nevertheless, some analysts felt Karpov had managed to use his scant forces to create an impregnable defense. To win, the champion had to maneuver adroitly to position his own king on the e7 square to further trap the black king.

Under the tournament schedule, the opponents were to start Game 17 on Monday before resuming the adjourned match. But Kasparov took the second of his three allotted timeouts to put off Game 17 and used the respite to find the winning route.

Play opened yesterday with the unsealing of Kasparov's adjourned 89th move. It was Ra7, the start of a paradoxical retreat of the rook that soon broke up Karpov's tight defense.

After Kasparov's 96th move, Bc3, black faced a chess player's despair -- zugzwang -- forced to damage his position no matter what move he made. Kasparov reached the victory square, king to e7, on his 102nd and final move. Karpov was left with no defense against check on the eighth rank and mate almost immediately after that.

The 17th game is scheduled for today, but there was speculation that Karpov would use the second of his three timeouts to regroup.

At this point, both players seem to lack energy and may be exhausted. One former world champion, Boris Spassky, characterized the play until now as "not as high as in other world championship matches but with a lot of fighting going on in every game."

The first player to reach 12 1/2 points wins $1.7 million of a $3 million prize; if the match ends in a tie, the two players split the pot.

Despite Kasparov's strong advantage, there is precedent for a comeback by Karpov: In their last championship match, in 1987, Kasparov held a similar lead at the same stage of the competition. Karpov then rallied strongly and the match was decided by a dramatic win by Kasparov in the 24th and final game.

Kavalek is an international grandmaster. Sussman is a Washington writer and opinion analyst. For results of the latest World Chess Championship game, call Post-Haste at 202-334-9000 on a Touch-Tone phone and enter code 8000. The service is free.