LONDON (AP) _ Former champion Anatoly Karpov begins a 16-game match in Spain on Tuesday with fellow Soviet Andrei Sokolov for the right to challenge Garri Kasparov for the world chess title.

Karpov, who held the championship for 10 years, will be fighting for another chance to regain the title he lost to Kasparov in November 1985.

At 23, Sokolov is 12 years younger than his opponent. He has stormed past the game's top players to become the third-ranked player in the world.

The victor will be the first to score 8 1/2 points. A victory scores one point, and each player gets one-half point for a draw.

Experts give Karpov the edge against Sokolov because of the former champion's vast experience, including 96 championship games against Kasparov and two successful title defenses in 1978 and 1981 against Victor Korchnoi, a Soviet defector who now plays for Switzerland.

As champion, his cool manner and creeping style netted him a record number of tournament victories.

Sokolov is a student at the prestigious Sports Institute in Moscow. He shot to attention after winning the 1982 world junior championship in Copenhagen, followed by a dramatic victory in the Soviet championship two years later.

In 1985 he tied for first in the world championship candidates tournament in Montpelier, France, and defeated Soviet grandmasters Rafael Vaganian and Artur Yusupov in play-off matches.

Sokolov is three weeks older than Kasparov, whose brilliant and bitter personal duels with Karpov grabbed the world's attention.

A recent poll among grandmasters for the French chess magazine gave Karpov a 60 per cent chance to beat Sokolov and face Kasparov for a fourth time.

But Sokolov said in an interview in the magazine: ''I've won all the matches where I was not the favorite. If these prognostications are the same, then the result will be the same.''

The match will be in Linares, a town in the Andalusian region of southern Spain.

No date or venue has been set for Kasparov's autumn title match with the winner of the Karpov-Sokolov duel.

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EDITOR'S NOTE - David Goodman covered all three Karpov-Kasparov title matches for The Associated Press and will be in Linares for the Karpov-Sokolov match.